Implementing test for lightning in pennylane

[PietropaoloFrisoni]

Context: This PR should be merged after this one is merged in pennylane-lightning. That is, after the jaxpr_jvp method has been implemented for lightning devices, so that we can compute gradients with lightning.qubit

Description of the Change: As above.

Benefits: We can differentiate using lightning.qubit

Possible Drawbacks: None.

Related GitHub Issues: None.

[sc-86927]

[github-actions]

Hello. You may have forgotten to update the changelog!
Please edit doc/releases/changelog-dev.md 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.

[andrijapau]

Nice! 🚀

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.62%. Comparing base (3f589f8) to head (6d42f13).
Report is 348 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7125   +/-   ##
=======================================
  Coverage   99.62%   99.62%           
=======================================
  Files         503      503           
  Lines       49024    49024           
=======================================
  Hits        48839    48839           
  Misses        185      185           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.