Add deployment targets to the package manifest (#2082)

Motivation:

Core components of grpc-swift v2 require API from the latest SDKs. This
causes a proliferation of availability annotations through our API.
Rather than doing this we can set the minimum platforms in the package
manifest.

Modifications:

- Remove availability annotations
- Set platforms in the package manifest

Result:

- Less boilerplate
- Users must set platforms in their package manifest

Author: glbrntt

Examples/echo/Sources/Subcommands/Serve.swift

@@ -42,7 +42,6 @@ struct Serve: AsyncParsableCommand {
   }
 }
 
-@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
 struct EchoService: Echo_Echo_ServiceProtocol {
   func get(
     request: ServerRequest<Echo_EchoRequest>,

Examples/route-guide/Sources/RouteGuide.swift

@@ -17,7 +17,6 @@
 import ArgumentParser
 
 @main
-@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
 struct RouteGuide: AsyncParsableCommand {
   static let configuration = CommandConfiguration(
     commandName: "route-guide",

Package.swift

@@ -105,6 +105,13 @@ let targets: [Target] = [
 
 let package = Package(
   name: "grpc-swift",
+  platforms: [
+    .macOS(.v15),
+    .iOS(.v18),
+    .tvOS(.v18),
+    .watchOS(.v11),
+    .visionOS(.v2),
+  ],
   products: products,
   dependencies: dependencies,
   targets: targets

Sources/GRPCCore/Call/Client/CallOptions.swift

@@ -21,7 +21,6 @@
 ///
 /// You can create the default set of options, which defers all possible
 /// configuration to the transport, by using ``CallOptions/defaults``.
-@available(macOS 13.0, iOS 16.0, watchOS 9.0, tvOS 16.0, *)
 public struct CallOptions: Sendable {
   /// The default timeout for the RPC.
   ///
@@ -108,7 +107,6 @@ public struct CallOptions: Sendable {
   }
 }
 
-@available(macOS 13.0, iOS 16.0, watchOS 9.0, tvOS 16.0, *)
 extension CallOptions {
   /// Default call options.
   ///
@@ -125,7 +123,6 @@ extension CallOptions {
   }
 }
 
-@available(macOS 13.0, iOS 16.0, watchOS 9.0, tvOS 16.0, *)
 extension CallOptions {
   package mutating func formUnion(with methodConfig: MethodConfig?) {
     guard let methodConfig = methodConfig else { return }

Sources/GRPCCore/Call/Client/ClientInterceptor.swift

@@ -88,7 +88,6 @@
 /// ```
 ///
 /// For server-side interceptors see ``ServerInterceptor``.
-@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
 public protocol ClientInterceptor: Sendable {
   /// Intercept a request object.
   ///

Sources/GRPCCore/Call/Client/ClientRequest.swift

@@ -61,7 +61,6 @@ public struct ClientRequest<Message: Sendable>: Sendable {
 ///
 /// See ``ClientRequest`` for single-message requests and ``StreamingServerRequest`` for the
 /// servers representation of a streaming-message request.
-@available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *)
 public struct StreamingClientRequest<Message: Sendable>: Sendable {
   /// Caller-specified metadata sent to the server at the start of the RPC.
   ///

Sources/GRPCCore/Call/Client/ClientResponse.swift

@@ -198,7 +198,6 @@ public struct ClientResponse<Message: Sendable>: Sendable {
 ///   print("RPC failed with code '\(error.code)'")
 /// }
 /// ```
-@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
 public struct StreamingClientResponse<Message: Sendable>: Sendable {
   public struct Contents: Sendable {
     /// Metadata received from the server at the beginning of the response.
@@ -325,7 +324,6 @@ extension ClientResponse {
   }
 }
 
-@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
 extension StreamingClientResponse {
   /// Creates a new accepted response.
   ///

Sources/GRPCCore/Call/Client/Internal/ClientRPCExecutor+HedgingExecutor.swift

@@ -16,7 +16,6 @@
 
 public import Synchronization  // would be internal but for usableFromInline
 
-@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
 extension ClientRPCExecutor {
   @usableFromInline
   struct HedgingExecutor<
@@ -62,7 +61,6 @@ extension ClientRPCExecutor {
   }
 }
 
-@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
 extension ClientRPCExecutor.HedgingExecutor {
   @inlinable
   func execute<R: Sendable>(
@@ -545,15 +543,13 @@ extension ClientRPCExecutor.HedgingExecutor {
   }
 }
 
-@available(macOS 13.0, iOS 16.0, watchOS 9.0, tvOS 16.0, *)
 @usableFromInline
 enum _HedgingTaskResult<R: Sendable>: Sendable {
   case rpcHandled(Result<R, any Error>)
   case finishedRequest(Result<Void, any Error>)
   case timedOut(Result<Void, any Error>)
 }
 
-@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
 @usableFromInline
 enum _HedgingAttemptTaskResult<R: Sendable, Output: Sendable>: Sendable {
   case attemptPicked(Bool)

Sources/GRPCCore/Call/Client/Internal/ClientRPCExecutor+OneShotExecutor.swift

@@ -14,7 +14,6 @@
  * limitations under the License.
  */
 
-@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
 extension ClientRPCExecutor {
   /// An executor for requests which doesn't apply retries or hedging. The request has just one
   /// attempt at execution.
@@ -54,7 +53,6 @@ extension ClientRPCExecutor {
   }
 }
 
-@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
 extension ClientRPCExecutor.OneShotExecutor {
   @inlinable
   func execute<R: Sendable>(
@@ -90,7 +88,6 @@ extension ClientRPCExecutor.OneShotExecutor {
   }
 }
 
-@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
 extension ClientRPCExecutor.OneShotExecutor {
   @inlinable
   func _execute<R: Sendable>(
@@ -129,7 +126,6 @@ extension ClientRPCExecutor.OneShotExecutor {
   }
 }
 
-@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
 @inlinable
 func withDeadline<Result: Sendable>(
   _ deadline: ContinuousClock.Instant,

Sources/GRPCCore/Call/Client/Internal/ClientRPCExecutor+RetryExecutor.swift

@@ -14,7 +14,6 @@
  * limitations under the License.
  */
 
-@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
 extension ClientRPCExecutor {
   @usableFromInline
   struct RetryExecutor<
@@ -60,7 +59,6 @@ extension ClientRPCExecutor {
   }
 }
 
-@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *)
 extension ClientRPCExecutor.RetryExecutor {
   @inlinable
   func execute<R: Sendable>(
@@ -302,7 +300,6 @@ extension ClientRPCExecutor.RetryExecutor {
   }
 }
 
-@available(macOS 13.0, iOS 16.0, watchOS 9.0, tvOS 16.0, *)
 @usableFromInline
 enum _RetryExecutorTask<R: Sendable>: Sendable {
   case timedOut(Result<Void, any Error>)