benchmark of validx library

[mathbeal]

Comparing similar libraries is encouraged on pydantic benchmark page https://pydantic-docs.helpmanual.io/benchmarks/

Change Summary

• test_validx.py added to compare performance of validx library against pydantic
• datetime.now() replaced by time.perf_counter (see https://docs.python.org/3/library/time.html#time.perf_counter)

Related issue number

closes #1816

Checklist

• Unit tests for the changes exist
• Tests pass on CI and coverage remains at 100%
• Documentation reflects the changes where applicable
• changes/<pull request or issue id>-<github username>.md file added describing change
  (see changes/README.md for details)

[codecov]

Codecov Report

Merging #1810 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master     #1810   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           21        21           
  Lines         3895      3895           
  Branches       783       783           
=========================================
  Hits          3895      3895           

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[samuelcolvin]

Sorry for the slow response, and sorry to disappoint, but I'm afraid I'm not accepting benchmarks for libraries that are significantly less popular than pydantic itself, see #1939 (comment) for an explanation, see also #1525.

Now that I've made that rule and refused a number of other libraries, I can't really accept validx.

[samuelcolvin]

happy to accept a tweak to the wording on the benchmarks page to make this clear, so people don't waste their time.

I feel really bad closing pull requests like this. 🙏