This allows makes the distinction between cachable and non-cachable properties cleaner and allows us to more easily compute contextual information (like type relations) for cached items later.
'available(..., deprecated: <version>)'. If the version is larger than the
current active version, the declaration is "soft deprecated". Emit a
relevant diagnostics for those items. If the version is equal to or
larger than '100000.0', it means the distant future without specifying
the version.
rdar://76122625
* Implement 'getDiagnosticSeverity()' and 'getDiagnosticMessage()' on
'CodeCompletionResult'
* Differentiate 'RedundantImportIndirect' from 'RedundantImport'
* Make non-Sendable check respects '-warn-concurrency'
rdar://76129658
