Add qml.workflow.construct_execution_config(qnode)(*args,**kwargs)

[andrijapau]

Context:

The execution configuration of a particular QNode instance is needed in our source code occasionally for various things (such as getting the gradient function).

Description of the Change:

This PR introduces a new helper function in the workflow module. Specifically,

• Interface is updated in _resolve_execution_config
• Added str dunder method for prettier printing

@qml.qnode(qml.device("default.qubit", wires=1))
def circuit(x):
    qml.RX(x, 0)
    return qml.expval(qml.Z(0))

>>> config = qml.workflow.construct_execution_config(circuit)(1)
>>> pprint.pprint(config)
ExecutionConfig(grad_on_execution=False,
                use_device_gradient=True,
                use_device_jacobian_product=False,
                gradient_method='backprop',
                gradient_keyword_arguments={},
                device_options={'max_workers': None,
                                'prng_key': None,
                                'rng': Generator(PCG64) at 0x17D5BB220},
                interface=<Interface.AUTO: 'auto'>,
                derivative_order=1,
                mcm_config=MCMConfig(mcm_method=None, postselect_mode=None),
                convert_to_numpy=True)

Benefits: Simplifies some code found in specs.py and construct_batch.py.

Possible Drawbacks: None.

[sc-83343]

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.59%. Comparing base (58d4f4f) to head (90e36cf).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6901   +/-   ##
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  Coverage   99.59%   99.59%           
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  Files         478      479    +1     
  Lines       45295    45317   +22     
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+ Hits        45113    45135   +22     
  Misses        182      182           

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[albi3ro]

❤️ This has made me realize we should set the interface in _resolve_execution_config, but that can be a follow on.

I have a feeling this is going to be really useful.