Use pyo3-stub-gen to support IDE type hints

[cardigan1008]

For #304 .

This PR introduces the use of pyo3-stub-gen to automatically generate .pyi files. These stub files provide type hints for Python IDEs.

Currently, the following modules are supported:

• Epoch
• TimeScale
• TimeSeries
• Duration
• LatestLeapSeconds
• LeapSecondsFile
• Ut1Provider
• PyHifitimeError
• PyDurationError
• PyParsingError

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 83.94%. Comparing base (93192da) to head (9755059).
Report is 15 commits behind head on master.

Files with missing lines	Patch %	Lines
src/bin/stub_gen.rs	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #329      +/-   ##
==========================================
- Coverage   84.01%   83.94%   -0.07%     
==========================================
  Files          22       23       +1     
  Lines        3691     3694       +3     
==========================================
  Hits         3101     3101              
- Misses        590      593       +3     

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[ChristopherRabotin]

It seems that the stub generator could not find any of the functions in any of the classes, so as-is this new pyi file won't help IDE users in autocompleting.

[cardigan1008]

Yes. So maybe we can turn to another way to do this, like dora's?

[ChristopherRabotin]

I like that dora's approach uses the package introspection, but I could not seem to get it to work correctly when I tried a few weeks (months?) ago. It kept on complaining that one of the return types was not defined although I thought I had. Feel free to give it a try of course!