* [CSDiagnostics] Handle arg to param generic when locator points to ConstraintLocator::GenericArgument
* [test] Add SR-12242 test case
* [CSDiagnostics] Handle arg to param on Generic mismatch as a fallback diagnostic
* [CSDiagnostics] Make assign diagnostics in GenericMismatchFailure handle more cases
* [test] Adding test cases for assign expr in GenericMismatch diagnostics
* [CSDiagnostics] Improving inout to pointer argument conversions with optionals diagnostics
These include the pointer-to-pointer and pointer-to-buffer-pointer
initialiser parameters amongst a couple of others, such as
`Unmanaged.fromOpaque`, and the source for the `move[...]` family of
methods.
The existing verification seems unnecessarily brittle, but this isn't
a general fix for that problem. This fixes one instance of where we
are generating perfectly valid pointer conversions that the verifier
is currently blowing up on.
I've opened https://bugs.swift.org/browse/SR-8264 to track reworking
this verification to not be quite so brittle.
