fix #23262 - [REG v2.113.0-beta.1] ICE when trying to cast a class instance to a C++ interface

[rainers]

no need to exclude C++ classes/interfaces from runtime cast target

[dlang-bot]

Thanks for your pull request, @rainers!

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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 "stable + dmd#23263"

[ibuclaw]

This fails going the other way though, as C++ interfaces don't contain an Interface record.

    auto dpl = cast(class23262)(cpp);
    assert(dpl);

[rainers]

Yes, casting from C++ to D classes is not supported. I can add that test, too, if it makes the direction clearer.