This was disabled explicitly in recent commit
232c948674cff1b4b72c2d6b3acfa7342d096dd1 to prevent using
the <compare> header from STL.
Now, re-enabling by implementing an ETL version of it in compare.h
* Add eq and ne operators
* Add three-way comparison to compare utils.
* Three-way comparison test now using own test data.
* Rename test struct for three-way comparison test.
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Co-authored-by: grigorev <grigorev@protei.ru>