swift

933f8eb8 - [Concurrency] Split up the non-Sendable argument diagnostics and improve

[Concurrency] Split up the non-Sendable argument diagnostics and improve wording. Splitting up the diagnostic into separate diagnostics based on the reference kind is easier for me to read. The wording of the error message now puts the problem -- crossing an isolation boundary -- at the center of the message, and attempts to clarify how the value crosses an isolation boundary. E.g. for the witness diagnostics, the value crosses an isolation boundary when calling the witness through the protocol requirement in generic code. This change does not add any additional information to the diagnostics, but it'd be valuable to show both the source and destination isolation.