Allow to disable use of [[no_unique_address]] attribute

[hkaiser]

The CMake configuration variable HPX_WITH_SUPPORT_NO_UNIQUE_ADDRESS can be used to disable the [[no_unique_address]] attribute in cases when HPX is compiled using MSVC but the code using it is compiled using clang-cl (which doesn't support this attribute on Windows before V18).

HPX_WITH_SUPPORT_NO_UNIQUE_ADDRESS defaults to ON.

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
✅ +0.49%	✅ 100.00%

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (c374f26)	397874	336695	84.62%
Head commit (ee2f3df)	190197 (-207677)	161870 (-174825)	85.11% (+0.49%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#6404)	1	1	100.00%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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_{You may notice some variations in coverage metrics with the latest Coverage engine update. For more details, visit the documentation}