[stable] Revert "Fix Issue 19754 - cast() sometimes yields lvalue, sometimes yields rvalue"

[kinke]

Reverts #9505, an incomplete bugfix (see the discussion in that PR), for a sane 2.087 state, primarily for LDC and GDC. Fixing this properly will likely require breaking changes (#10124) and so land post-2.087. Pinging @RazvanN7 and @ibuclaw.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	19754	normal	cast() sometimes yields lvalue, sometimes yields rvalue

Testing this PR locally

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

dub fetch digger
dub run digger -- build "stable + dmd#10220"

[ibuclaw]

What about #10115?

[ibuclaw]

Actually, nevermind. It's an independent bug-fix,

[kinke]

#10115 is still in there, and not totally independent, but I'll try to revert those select diagnostics for some special cases in a later version of #10124, as they shouldn't be required anymore (but the additional test cases will stay).