[Refactoring] [test] Use more strict matching on returns and breaks

Make sure we match against an exact return or
break in these cases, rather than a placeholder.

Author: hamishknight

test/refactoring/ConvertAsync/convert_function.swift

@@ -87,7 +87,7 @@ func asyncParams(arg: String, _ completion: (String?, Error?) -> Void) {
 // ASYNC-SIMPLE: func {{[a-zA-Z_]+}}(arg: String) async throws -> String {
 // ASYNC-SIMPLE-NEXT: let str = try await simpleErr(arg: arg)
 // ASYNC-SIMPLE-NEXT: print("simpleErr")
-// ASYNC-SIMPLE-NEXT: return str
+// ASYNC-SIMPLE-NEXT: {{^}}return str{{$}}
 // ASYNC-SIMPLE-NEXT: print("after")
 // ASYNC-SIMPLE-NEXT: }
 
@@ -120,7 +120,7 @@ func asyncResNewErr(arg: String, _ completion: (Result<String, Error>) -> Void)
 // ASYNC-ERR-NEXT: do {
 // ASYNC-ERR-NEXT: let str = try await simpleErr(arg: arg)
 // ASYNC-ERR-NEXT: print("simpleErr")
-// ASYNC-ERR-NEXT: return str
+// ASYNC-ERR-NEXT: {{^}}return str{{$}}
 // ASYNC-ERR-NEXT: print("after")
 // ASYNC-ERR-NEXT: } catch let err {
 // ASYNC-ERR-NEXT: throw CustomError.Bad
@@ -142,11 +142,11 @@ func asyncUnhandledCompletion(_ completion: (String) -> Void) {
 // ASYNC-UNHANDLED: func asyncUnhandledCompletion() async -> String {
 // ASYNC-UNHANDLED-NEXT: let str = await simple()
 // ASYNC-UNHANDLED-NEXT: let success = run {
-// ASYNC-UNHANDLED-NEXT: <#completion#>(str)
-// ASYNC-UNHANDLED-NEXT: return true
+// ASYNC-UNHANDLED-NEXT:   <#completion#>(str)
+// ASYNC-UNHANDLED-NEXT:   {{^}} return true{{$}}
 // ASYNC-UNHANDLED-NEXT: }
 // ASYNC-UNHANDLED-NEXT: if !success {
-// ASYNC-UNHANDLED-NEXT: return "bad"
+// ASYNC-UNHANDLED-NEXT: {{^}} return "bad"{{$}}
 // ASYNC-UNHANDLED-NEXT: }
 // ASYNC-UNHANDLED-NEXT: }