Enable more MainActor code paths for Embedded Swift

Author: MaxDesiatov

stdlib/public/Concurrency/Executor.swift

@@ -36,11 +36,9 @@ public protocol Executor: AnyObject, Sendable {
   func enqueue(_ job: consuming ExecutorJob)
   #endif // !SWIFT_STDLIB_TASK_TO_THREAD_MODEL_CONCURRENCY
 
-  #if !$Embedded
   /// `true` if this is the main executor.
   @available(StdlibDeploymentTarget 6.2, *)
   var isMainExecutor: Bool { get }
-  #endif
 }
 
 @available(StdlibDeploymentTarget 6.2, *)
@@ -145,12 +143,10 @@ extension Executor where Self: Equatable {
 
 extension Executor {
 
-  #if !$Embedded
   // This defaults to `false` so that existing third-party Executor
   // implementations will work as expected.
   @available(StdlibDeploymentTarget 6.2, *)
   public var isMainExecutor: Bool { false }
-  #endif
 
 }
 
@@ -368,7 +364,7 @@ public protocol SerialExecutor: Executor {
 @available(StdlibDeploymentTarget 6.0, *)
 extension SerialExecutor {
 
-  #if !$Embedded && !SWIFT_STDLIB_TASK_TO_THREAD_MODEL_CONCURRENCY
+  #if !SWIFT_STDLIB_TASK_TO_THREAD_MODEL_CONCURRENCY
   @available(StdlibDeploymentTarget 6.2, *)
   public var isMainExecutor: Bool { return MainActor.executor._isSameExecutor(self) }
   #endif
@@ -579,11 +575,9 @@ public protocol MainExecutor: RunLoopExecutor, SerialExecutor {
 /// executors.
 @available(StdlibDeploymentTarget 6.2, *)
 public protocol ExecutorFactory {
-  #if !$Embedded
   /// Constructs and returns the main executor, which is started implicitly
   /// by the `async main` entry point and owns the "main" thread.
   static var mainExecutor: any MainExecutor { get }
-  #endif
 
   /// Constructs and returns the default or global executor, which is the
   /// default place in which we run tasks.
@@ -596,7 +590,7 @@ typealias DefaultExecutorFactory = PlatformExecutorFactory
 @available(StdlibDeploymentTarget 6.2, *)
 @_silgen_name("swift_createExecutors")
 public func _createExecutors<F: ExecutorFactory>(factory: F.Type) {
-  #if !$Embedded && !SWIFT_STDLIB_TASK_TO_THREAD_MODEL_CONCURRENCY
+  #if !SWIFT_STDLIB_TASK_TO_THREAD_MODEL_CONCURRENCY
   MainActor._executor = factory.mainExecutor
   #endif
   Task._defaultExecutor = factory.defaultExecutor