Disable CI for draft PRs

[anthayes92]

Context:
Tooling Team has requested that all CI checks for draft PRs across all PennyLane repos are to be disabled to free up GH runner resources. SC Story.

Description of the Change:
Conditions for checking whether a PR is in draft state have been added to existing workflows.

Benefits:
Reduces GH runner usage.

Possible Drawbacks:
Some development steps are deferred to PRs in "ready for review" state only.

Related GitHub Issues:
N/A

Verification:

Created this PR as draft, only lightweight CI checks use GitHub runners (formatting, changelog reminder). When marked as "ready for review" the CI checks ran (excluding wheel builds and multi-gpu runners). When labels added for wheel builds and multi-gpu runners all CI checks ran.

[github-actions]

Hello. You may have forgotten to update the changelog!
Please edit .github/CHANGELOG.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.

[AmintorDusko]

Can we have a label that could re-enable CIs for draft PRs?
We rely a lot on our CI/CD workflows.

[mlxd]

Can we have a label that could re-enable CIs for draft PRs? We rely a lot on our CI/CD workflows.

This was a long-time coming request. We can enable the CI by going out of draft mode.
Given the burden the CI has right now, tests are to run in non-draft mode across the org by default.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.34%. Comparing base (dd5dca1) to head (b75cd06).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #847      +/-   ##
==========================================
+ Coverage   97.59%   98.34%   +0.75%     
==========================================
  Files         117      151      +34     
  Lines       18642    23636    +4994     
==========================================
+ Hits        18193    23244    +5051     
+ Misses        449      392      -57     

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[Mandrenkov]

I think there might be a couple of cases where we need careful about operator precedence but otherwise this looks good. 👍

[anthayes92]

Reran CI in "draft" and "ready for review" after adding @Mandrenkov suggestions on operator ordering, all works as expected.

[Mandrenkov]

Thanks @anthayes92, just want to confirm the new if conditions work correctly with push and workflow_call events before approving!

[vincentmr]

Just a style suggestion, but looks good to me. Thanks @anthayes92 !

[mlxd]

Hey @anthayes92
Is this good to be merged?

[anthayes92]

Hey @anthayes92 Is this good to be merged?

Similar reason as mentioned here, though since you have a higher stake in the lightning repo perhaps you'd like to make the call?

[Alex-Preciado]

Let's go ahead and merge this one and also the PennyLane PR (PennyLaneAI/pennylane#6093). We can add a label to run tests in draft mode in a follow-up PR.