Concurrency: Move PackExpansionType check to swift::diagnoseNonSendableTypes()
This was added in #80220 to fix a related issue with captures of packs,
but it's even better to sink this down into diagnoseNonSendableTypes(),
so that we can handle packs in parameter position as well.
- Fixes https://github.com/swiftlang/swift/issues/82614.
- Fixes rdar://problem/154649522.