Allow custom implementations of nb_kernel_name and nb_language in papermill engines

[rohitsanj]

Context behind this PR

At Noteable, we came across a use-case where parametrized executions with a custom Noteable engine were not working because papermill expects the kernel_name to be present in the kernelspec of the notebook if kernel_name was not explicitly passed in as a kwarg. It throws a ValueError with the message "No kernel name found in notebook and no override provided.". Like so,

>>> pm.execute_notebook(
        f'noteable://{file_id}', 
        'foo.ipynb', 
        engine_name='noteable'
        # custom Noteable kwargs
        file=file, 
        client=client, 
        log_output=True,
    )
...
ValueError: No kernel name found in notebook and no override provided.

What does this PR do?

This PR allows the extended engine to define custom business logic for the following:

• fetching kernel name from the notebook object by implementing the nb_kernel_name method
• fetching programming language from the notebook object by implementing the nb_language method

[codecov]

Codecov Report

Merging #676 (c4271aa) into main (98013f0) will increase coverage by 0.05%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #676      +/-   ##
==========================================
+ Coverage   91.72%   91.78%   +0.05%     
==========================================
  Files          17       17              
  Lines        1583     1594      +11     
==========================================
+ Hits         1452     1463      +11     
  Misses        131      131              

Impacted Files	Coverage Δ
papermill/engines.py	98.37% <100.00%> (+0.09%)	⬆️
papermill/execute.py	100.00% <100.00%> (ø)
papermill/parameterize.py	98.00% <100.00%> (+0.04%)	⬆️

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