(Closes 2311) Add functionality to derive module and subroutine names of adjoint test from filename for LFRic API

[DrTVockerodtMO]

Closes #2311 which has a description of the problem.

Patch notes

I solved the problem by feeding the filename given to -otest down into the codebase. Here is a summary of the changes made across the relevant call tree:

src/psyclone/psyad/main.py
Changed the default value of this variable to be None. Added in the args.test_filename value to the call signature of generate_adjoint_str.

src/psyclone/psyad/tl2ad.py
Added new test_filename argument into call signature. I decided to add the conversion of the test_filename into the test_name variable here because I figured it would be API specific, so having it in the API selection telegraphs that nicely. Default value is just adjoint_test like the previous behaviour.

For the LFRic API, we take everything from test_filename before "_mod." to be the test_name.

src/psyclone/psyad/domain/lfric/lfric_adjoint_harness.py
Changed function to use test_name instead of the hardcoded value of "adjoint_test".

Testing

I tested this by making changes to src/psyclone/tests/psyad/domain/lfric/test_lfric_adjoint_harness.py. I passed in a new value of the optional test_name that is "adjoint_test_alg" which would replicate what we see in LFRic. This test passed by producing the expected "adjoint_test_alg_mod" as the module name and "adjoint_test_alg" as the subroutine name.

I also tested this by changing src/psyclone/tests/psyad/tl2ad_test.py to include a test_filename KGO, which also passed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.86%. Comparing base (59668bb) to head (98fe8d6).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2749   +/-   ##
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  Coverage   99.86%   99.86%           
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  Files         354      354           
  Lines       48963    48966    +3     
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+ Hits        48899    48902    +3     
  Misses         64       64           

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