Clean-up Wires object usage across source code

[andrijapau]

Context:

Follow up to #6713.

It is not possible to initialize a Wires object with wires=None after #6713. However, we should not be using wires=None in our code-base unless it's appropriate.

Description of the Change:

This PR reviews the code-base to ensure that wires=None does not occur where it is not applicable. When appropriate, it updates the default to wires=() or uses no default at all.

Benefits: Code clean-up.

Possible Drawbacks: None identified.

[sc-78998]

[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.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.60%. Comparing base (585767c) to head (7c3a7d9).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6689   +/-   ##
=======================================
  Coverage   99.60%   99.60%           
=======================================
  Files         475      475           
  Lines       45102    45115   +13     
=======================================
+ Hits        44925    44938   +13     
  Misses        177      177           

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[lillian542]

I left a few small comments here and there, see what you think :)

[PietropaoloFrisoni]

Thanks! Just one clarification from me.

Regarding the discussion about changelog entries, can we have a unique changelog entry for all the improvements you implemented regarding the tests?

[lillian542]

Thanks for tidying this up :)

[PietropaoloFrisoni]

🚀