fix measurements with dynamic wires

[josephleekl]

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---

Context:
Currently when using dynamically determined wire count (e.g. qml.device("lightning.qubit") or qml.device("lightning.qubit", shots = x)), we have an issue when we perform measurements without specifying any observables or wires, i.e.

• qml.probs()
• qml.counts()
• qml.sample()

incorrect result is returned, since the number of wires is not known.

Description of the Change:
For measurements with no wires (i.e. no observables or wires provided), we edit the measurement process to include the number of wires. This is fixed for with and without shots.

Benefits:
Get correct results.

Possible Drawbacks:

Related GitHub Issues:
fixes #1086

[sc-85837]

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.08%. Comparing base (b16bfb1) to head (fba516f).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1081      +/-   ##
==========================================
+ Coverage   96.00%   99.08%   +3.07%     
==========================================
  Files         232      111     -121     
  Lines       39306    17114   -22192     
==========================================
- Hits        37737    16957   -20780     
+ Misses       1569      157    -1412     

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[AmintorDusko]

Good job! Nice integration with the tests we already have in place.
I'm assuming the coverage is showing false positives as usual. Please triple-check. (quadruplet-check?)

[maliasadi]

Thanks @josephleekl! Happy to approve 🙌