Added a separate pylintrc for labs tests

[rashidnhm]

Context: Adding a separate pylintrc for pennylane labs tests

Description of the Change:
This PR adds a new pylintrc file for pennylane labs tests.

The pennylane/labs/tests directory is excluded from linting from the root pylintrc file, this is required as the tests reside within pennylane folder itself.

The tests/.pylintrc file was copied over to be used for labs. The reason for introducing a new file instead of using the existing one in tests/ is so it allows us to easily diverge the configs in the future if necessary!

A new workflow was introduced that will only run if pennylane/labs/** was updated

Benefits:
Separate linting for labs.

Possible Drawbacks:

Related GitHub Issues:
sc-77561

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.34%. Comparing base (e710ca6) to head (25c5019).
Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6553      +/-   ##
==========================================
+ Coverage   99.17%   99.34%   +0.16%     
==========================================
  Files         456      456              
  Lines       43254    43273      +19     
==========================================
+ Hits        42899    42989      +90     
+ Misses        355      284      -71     

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[Jaybsoni]

Looks good to me, thanks @rashidnhm !

[mudit2812]

Looks good. I left one suggestions about adding black and isort to the same workflow. Otherwise LGTM. That codefactor issue is weird as well. Looks like a pylint bug that was resolved in 2.7.5 (context). We use 2.7.4 🫠

[mudit2812]

One final comment, otherwise ready to go.