Store whether a result is async in the `ContextFreeCodeCompletionResult` and determine whether an async method is used in a sync context when promoting the context free result to a contextual result.
rdar://78317170
Generating diagnostics for "not recommended" items requires an
associated declaration. However, cases like this:
func test(fn: (Int) async -> Void) {
fn(#^HERE^#)
}
For the function call pattern item, there's no associated decl because
the callee is an expression. Ideally it should emit a diagnostic, but
for now, to avoid the crash, don't emit diagnostics unless the item has
the associated decl.
rdar://95306033
* Implement 'getDiagnosticSeverity()' and 'getDiagnosticMessage()' on
'CodeCompletionResult'
* Differentiate 'RedundantImportIndirect' from 'RedundantImport'
* Make non-Sendable check respects '-warn-concurrency'
rdar://76129658
