[interop][SwiftToCxx] experimentally expose Swift's Array type

This is done without annotations on the stdlib yet while @_expose is still experimental

test/Interop/SwiftToCxx/stdlib/array/array-execution.cpp

@@ -0,0 +1,46 @@
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+
+// RUN: %target-swift-frontend -parse-as-library %platform-module-dir/Swift.swiftmodule/%module-target-triple.swiftinterface -enable-library-evolution -disable-objc-attr-requires-foundation-module -typecheck -module-name Swift -parse-stdlib -enable-experimental-cxx-interop -emit-clang-header-path %t/Swift.h  -experimental-skip-all-function-bodies
+
+// RUN: %target-swift-frontend -typecheck %t/use-array.swift -typecheck -module-name UseArray -enable-experimental-cxx-interop -emit-clang-header-path %t/UseArray.h
+
+// RUN: %target-interop-build-clangxx -fno-exceptions -std=gnu++20 -c %t/array-execution.cpp -I %t -o %t/swift-stdlib-execution.o
+// RUN: %target-build-swift %t/use-array.swift -o %t/swift-stdlib-execution -Xlinker %t/swift-stdlib-execution.o -module-name UseArray -Xfrontend -entry-point-function-name -Xfrontend swiftMain
+// RUN: %target-codesign %t/swift-stdlib-execution
+// RUN: %target-run %t/swift-stdlib-execution | %FileCheck %s
+
+// REQUIRES: executable_test
+
+//--- use-array.swift
+@_expose(Cxx)
+public func createArray(_ val: CInt) -> [CInt] {
+    return [val, val]
+}
+
+@_expose(Cxx)
+public func passthroughArray(_ val: [CInt]) -> Array<CInt> {
+    return val
+}
+
+@_expose(Cxx)
+public func printArray(_ val: Array<CInt>) {
+    print(val)
+}
+
+//--- array-execution.cpp
+
+#include <cassert>
+#include "Swift.h"
+#include "UseArray.h"
+
+int main() {
+  using namespace Swift;
+
+  {
+    Array<int> val = UseArray::createArray(2);
+    UseArray::printArray(UseArray::passthroughArray(val));
+  }
+// CHECK: [2, 2]
+  return 0;
+}