Add new trait isCOMClass

[rikkimax]

I'm not 100% certain I got this right, if I haven't let me know what to fix.

[dlang-bot]

Thanks for your pull request and interest in making D better, @rikkimax! We are looking forward to reviewing it, and you should be hearing from a maintainer soon.
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• My PR is fully covered with tests (you can see the coverage diff by visiting the details link of the codecov check)
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• I have provided a detailed rationale explaining my changes
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[rikkimax]

Implementation PR: dlang/dmd#17095