Use isinstance(op, qml.Op) instead of operation.name string comparison in Python interfaces

[vincentmr]

Before submitting

Please complete the following checklist when submitting a PR:

• All new features must include a unit test.
  If you've fixed a bug or added code that should be tested, add a test to the
  tests directory!

• All new functions and code must be clearly commented and documented.
  If you do make documentation changes, make sure that the docs build and
  render correctly by running make docs.

• Ensure that the test suite passes, by running make test.

• Add a new entry to the .github/CHANGELOG.md file, summarizing the
  change, and including a link back to the PR.

• Ensure that code is properly formatted by running make format.

When all the above are checked, delete everything above the dashed
line and fill in the pull request template.

---

Context:
There are several places in Python interfaces that we use string comparison for comparing PL operations and observables.
String comparison is usually considered a bad practice in compare with using isinstance(object, class_type) in Python.

Description of the Change:
Use isinstance where possible.

Benefits:

Possible Drawbacks:

Related GitHub Issues:
[sc-58642]

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.67%. Comparing base (7ff0b52) to head (7970a4a).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #691      +/-   ##
==========================================
- Coverage   98.67%   98.67%   -0.01%     
==========================================
  Files         174      174              
  Lines       22625    22624       -1     
==========================================
- Hits        22326    22325       -1     
  Misses        299      299              

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

[AmintorDusko]

I think it looks good so far.
Do you have any idea why some CIs are failing?

[vincentmr]

I think it looks good so far. Do you have any idea why some CIs are failing?

I think it is just the usual: some wheel building failing and needs restart, codecov prematurely reporting before all Linux tests are over. I'll monitor.

[AmintorDusko]

Well, in terms of coding and general testing, your PR looks pretty good.
I will approve now, let me know if you need any help with the falling CIs.