Add tests for gafferpy helper functions

[t92549]

Tests should be added that assert helper functions still work for backwards compatibility.

Background

A lot of Operations in gafferpy have inner helper functions that make them easier to use.

For example, the following code wraps your inputs into a list of ElementSeeds:
https://github.com/gchq/gaffer-tools/blob/45f5fd1920bf5b93459f16df097224c1c2d0ed50/python-shell/src/gafferpy/gaffer_operations.py#L1123-L1136

This means you could provide an input of 1, but it will be wrapped as:
[{"class": "uk.gov.gchq.gaffer.operation.data.EntitySeed", "vertex": 1}]

These core Operations will now be generated and by default these helper functions will not be generated.

Therefore, there needs to be more tests to assert that the helper functions still work for backwards compatibility, so where they are missing they can be added to the generator code.