[ClangImporter] Enable parsing bounds safety attributes in C++

This allows combining __counted_by and std::span for safe interop.
Previously we disabled this in C++ mode due to issues when bounds
attributes occurred directly or indirectly in templated contexts, but
this has now been resolved on the clang side.

Author: hnrklssn

lib/ClangImporter/ClangImporter.cpp

@@ -566,8 +566,7 @@ void importer::getNormalInvocationArguments(
     }
   }
 
-  if (LangOpts.hasFeature(Feature::SafeInteropWrappers) &&
-      !LangOpts.EnableCXXInterop)
+  if (LangOpts.hasFeature(Feature::SafeInteropWrappers))
     invocationArgStrs.push_back("-fexperimental-bounds-safety-attributes");
 
   // Set C language options.

test/Interop/Cxx/stdlib/std-span-interface.swift

@@ -33,6 +33,10 @@ import CxxStdlib
 // CHECK-NEXT: @lifetime(borrow v)
 // CHECK-NEXT: @_alwaysEmitIntoClient @_disfavoredOverload public func funcWithSafeWrapper3(_ v: borrowing VecOfInt) -> Span<CInt>
 // CHECK-NEXT: @lifetime(p)
-// CHECK-NEXT: @_alwaysEmitIntoClient @_disfavoredOverload public func mixedFuncWithSafeWrapper1(_ p: UnsafePointer<Int32>!, _ len: Int32) -> Span<CInt>
-// CHECK-NEXT: @_alwaysEmitIntoClient public func mixedFuncWithSafeWrapper3(_ s: Span<CInt>, _ p: UnsafeMutablePointer<Int32>!, _ len: Int32)
-// CHECK-NEXT: @_alwaysEmitIntoClient public func mixedFuncWithSafeWrapper4(_ s: Span<CInt>, _ p: UnsafePointer<Int32>!, _ len: Int32)
+// CHECK-NEXT: @_alwaysEmitIntoClient public func mixedFuncWithSafeWrapper1(_ p: Span<Int32>) -> Span<CInt>
+// CHECK-NEXT: @lifetime(borrow v)
+// CHECK-NEXT: @_alwaysEmitIntoClient @_disfavoredOverload public func mixedFuncWithSafeWrapper2(_ v: borrowing VecOfInt, _ len: Int32) -> UnsafeBufferPointer<Int32>
+// CHECK-NEXT: @_alwaysEmitIntoClient public func mixedFuncWithSafeWrapper3(_ s: Span<CInt>, _ p: UnsafeMutableBufferPointer<Int32>)
+// CHECK-NEXT: @_alwaysEmitIntoClient public func mixedFuncWithSafeWrapper4(_ s: Span<CInt>, _ p: Span<Int32>)
+// CHECK-NEXT: @_alwaysEmitIntoClient public func mixedFuncWithSafeWrapper5(_ s: ConstSpanOfInt, _ p: Span<Int32>)
+// CHECK-NEXT: @_alwaysEmitIntoClient public func mixedFuncWithSafeWrapper6(_ s: ConstSpanOfInt, _ p: UnsafeMutableBufferPointer<Int32>)