Register plugins from entry points

[Ni-g-3l]

This PR is the same as : #1872 which I closed by error...

Sorry for inconvenient..

Old description

Hello

As suggest here I implemented the support of entrypoints in order to make the process of adding plugin to REZ easier.

Closes #1661

Feel free to add feedback !

Have a great day

[codecov]

Codecov Report

Attention: Patch coverage is 68.51852% with 17 lines in your changes missing coverage. Please review.

Project coverage is 60.09%. Comparing base (4708523) to head (f117b75).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/rez/plugin_managers.py	68.51%	12 Missing and 5 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1989      +/-   ##
==========================================
+ Coverage   60.02%   60.09%   +0.07%     
==========================================
  Files         163      163              
  Lines       20118    20151      +33     
  Branches     3506     3511       +5     
==========================================
+ Hits        12075    12110      +35     
+ Misses       7223     7220       -3     
- Partials      820      821       +1     

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[JeanChristopheMorinPerso]

@Ni-g-3l How did you recreate the branch? Some of my changes seem to be there, but my commits are not there... I'm confused.

[JeanChristopheMorinPerso]

I pushed my local branch to https://github.com/JeanChristopheMorinPerso/rez/tree/feat/register_plugin_from_entry_points_jc. Can you take it re-create a PR from it please? That will put us in the same state we were before.

[Ni-g-3l]

Sorry again ! Here is the new PR : #1991 (The last one I hope) with all of your commits and conflict fixed with master !

Thanks a lot !

[JeanChristopheMorinPerso]

Great, thanks a lot!