Add tests for issue 20761 - __traits(isSame) for alias tuples...

[MoonlightSentinel]

... is brokenand underspecified.

The original tests from #11373 got lost.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✗	20761	major	__traits(isSame) for alias tuples is broken and underspecified

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#11392"

[ghost]

can you add a test with varsious combination of nested AliasSeq ? e.g

AliasSeq!(0,AliasSeq!(1,2)) compared to AliasSeq!(0,1,2)) for example