Support for value_and_grad at the MLIR side (inside a jitting context)

[rauletorresc]

Context: Lowering of value_and_grad to MLIR is now supported when @qjit is used.

Description of the Change: A new ValueAndGradOp was added and the existing BackpropOp was modified to return two results: values and gradients.

Benefits: Code reutilization.

TODO:

• [ ] Add unit tests.
• [ ] Test corner cases.
• [ ] Update the changelog.md file

[sc-55116]

[github-actions[bot]]

Hello. You may have forgotten to update the changelog! Please edit doc/changelog.md on your branch with:

• A one-to-two sentence description of the change. You may include a small working example for new features.
• A link back to this PR.
• Your name (or GitHub username) in the contributors section.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 34.28571% with 23 lines in your changes missing coverage. Please review.

Project coverage is 99.25%. Comparing base (21e0f5f) to head (a2935a9). Report is 337 commits behind head on main.

Files with missing lines	Patch %	Lines
frontend/catalyst/jax_primitives.py	33.33%	16 Missing :warning:
frontend/catalyst/pennylane_extensions.py	36.36%	6 Missing and 1 partial :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #622      +/-   ##
==========================================
- Coverage   99.50%   99.25%   -0.26%     
==========================================
  Files          53       53              
  Lines        8930     8959      +29     
  Branches      655      658       +3     
==========================================
+ Hits         8886     8892       +6     
- Misses         25       47      +22     
- Partials       19       20       +1     

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[paul0403]

Closing this as value_and_grad is merged in by #804