These projections don't have access scopes, so the utility was treating them
like escapes.
Fixes: rdar://131499478 (Difficulties composing non-escapable types)
Add PartialApplyInst.hasNoescapeCapture
Add PartialApplyInst.mayEscape
Refactor DiagnoseInvalidEscapingCaptures. This may change functionality because tuples containing a noescape closure are now correctly recognized. Although I'm not sure such tupes can ever be captured directly.