Test supported gradient kwargs and raise error for shots kwarg

[dwierichs]

Context:
Additional kwargs passed to a QNode at initialization are interpreted as gradient kwargs.
They are checked against the hardcoded collection qml.gradients.SUPPORTED_GRADIENT_KWARGS to make sure that this boilerplate interpretation of additional kwargs makes sense.

Description of the Change:
This PR adds a test that makes sure that qml.gradients.SUPPORTED_GRADIENT_KWARGS actually matches all gradient transform kwargs supported by PL.
In addition, this PR introduces an error being raised when the keyword argument shots is passed at QNode initialization, because this is not a valid gradient kwarg and even if it were, it would lead to the confusing behaviour of QNode(..., shots=100) not executing with shots=100.

Benefits:
Code quality, better user input validation.

Possible Drawbacks:

Related GitHub Issues:
#5745

[sc-64175]

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.66%. Comparing base (456e474) to head (e3ed659).
Report is 256 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5748      +/-   ##
==========================================
- Coverage   99.67%   99.66%   -0.01%     
==========================================
  Files         414      414              
  Lines       39314    39023     -291     
==========================================
- Hits        39185    38893     -292     
- Misses        129      130       +1     

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[albi3ro]

🎉 Looks good :)

[PietropaoloFrisoni]

Thanks @dwierichs ! Looks amazing. Just a couple of minor comments, but no blockers from me 👍

[PietropaoloFrisoni]

Amazing! Thanks again @dwierichs