Support parameter broadcasting with GlobalPhase

[dwierichs]

Context:
GlobalPhase does not support broadcasting yet.

Description of the Change:
Introduce broadcasting to GlobalPhase, using the code from PauliRot with set(pauli_word) == {"I"}.
The latter falls back to the GlobalPhase implementation.

Also fixes a small bug where the global phase returned by one_qubit_decomposition gains a broadcasting dimension even if the input matrix does not have one.

Benefits:
Broadcasting support & Bug fix
Unlocks #4460

Possible Drawbacks:

Related GitHub Issues:
Implements #5815
Fixes #5880

[sc-65316]

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.65%. Comparing base (20eed81) to head (096312a).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff            @@
##           master    #5923    +/-   ##
========================================
  Coverage   99.65%   99.65%            
========================================
  Files         430      430            
  Lines       41505    41213   -292     
========================================
- Hits        41362    41072   -290     
+ Misses        143      141     -2     

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[astralcai]

Looks good, sorry about missing the part where broadcasting is tested for matrix.