Fix len parameter handling: Unit tests for gRPC and session

[batzuu]

• This contribution adheres to CONTRIBUTING.md.
• I've updated CHANGELOG.md if applicable.
• I've added tests applicable for this pull request

What does this Pull Request accomplish?

This PR is in the continuation of PR: Fixing size parameter handling and aims to add unit test for gRPC and session for the new nifake function added in the earlier PR.

• Adds necessary changes to enable gRPC calls for the new test method MultipleArraysDifferentSize in nifake.proto.
• Adds corresponding generated files, and tests (covered in testing section).

List issues fixed by this Pull Request

Adds to the validation for changes added to fix Issue 2137: Fix size parameter handling for functions with parameters referencing multiple size parameters.

What testing has been done?

• Unit test test_multiple_arrays_different_size added in nifake's test_grpc.py and test_session.py for validation.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.59%. Comparing base (cf435c0) to head (4b6fe22).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2140      +/-   ##
==========================================
- Coverage   89.62%   89.59%   -0.04%     
==========================================
  Files          61       48      -13     
  Lines       17308    16051    -1257     
==========================================
- Hits        15513    14381    -1132     
+ Misses       1795     1670     -125     

Flag	Coverage Δ
nidcpowersystemtests	94.65% <ø> (+0.04%)	⬆️
nidcpowerunittests	?
nidigitalsystemtests	92.26% <ø> (ø)
nidigitalunittests	?
nidmmsystemtests	92.72% <ø> (ø)
nifakeunittests	?
nifgensystemtests	94.61% <ø> (ø)
nimodinstsystemtests	73.85% <ø> (ø)
nimodinstunittests	?
nirfsgsystemtests	76.53% <ø> (ø)
niscopesystemtests	92.94% <ø> (ø)
niscopeunittests	?
nisesystemtests	91.50% <ø> (ø)
niswitchsystemtests	82.03% <ø> (ø)
nitclksystemtests	94.87% <ø> (ø)
nitclkunittests	?

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see 17 files with indirect coverage changes

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