Fix issue 22967 - no return ref inference for extended return semantics

[dkorpel]

#13940 introduced proper 'extended return semantics' (returning by assigning to this / the first ref parameter) for return ref, but it didn't have inference yet unlike return scope (#9220).

[dlang-bot]

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	22967	enhancement	[dip1000] no return ref inference for extended return semantics

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + dmd#13952"