Allow tensor batching in numerical representations of Operators

[dwierichs]

This is one of multiple PRs that together introduce the capability of tensor-batching, which enables execution of circuits with parameters that have a (single) batch dimension.

• In this PR, we mostly adapt the Operator and Operation base classes as well as methods related to matrix and eigenvalue representations to handle a batch dimension properly.
• This does not include the operations in ops/qubit/qchem_ops.py yet.
• The operations that explicitly support tensor batching are collected in qml.ops.qubit.attributes.supports_tensorbatching.
• operation labels do not work properly yet with batched parameters, the parameters are skipped in this case.
• This PR in particular does not modify any device, so that no tensor-batching can be used at circuit level yet.

[sc-18891]

[codecov]

Codecov Report

Merging #2535 (fb1b5b9) into parameter-broadcasting-1 (8960bbb) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@                    Coverage Diff                    @@
##           parameter-broadcasting-1    #2535   +/-   ##
=========================================================
  Coverage                     99.58%   99.58%           
=========================================================
  Files                           244      244           
  Lines                         19677    19750   +73     
=========================================================
+ Hits                          19596    19669   +73     
  Misses                           81       81           

Impacted Files	Coverage Δ
pennylane/operation.py	96.90% <100.00%> (+0.06%)	⬆️
pennylane/ops/functions/matrix.py	100.00% <100.00%> (ø)
pennylane/ops/qubit/attributes.py	100.00% <100.00%> (ø)
pennylane/ops/qubit/matrix_ops.py	100.00% <100.00%> (ø)
pennylane/ops/qubit/parametric_ops.py	100.00% <100.00%> (ø)

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[josh146]

@dwierichs as discussed I removed my review here; simply re-tag me when you think it is ready for review again :)

[dwierichs]

Superseded by #2609 .