chore: split validation logic in smaller functions

[ferrarimarco]

Proposed changes

• Move USE_FIND_ALGORITHM and VALIDATE_ALL_CODEBASE validation in a dedicated function (ValidateFindMode).
• Move ANSIBLE_DIRECTORY validation to a dedicated function (ValidateAnsibleDirectory).
• Move VALIDATE_xxxx variables validation to a dedicated function (ValidateValidationVariables).
• Mark ANY_SET, ANY_TRUE, ANY_FALSE as local because we don't need to reference them anywhere outside ValidateValidationVariables.
• Add some debug statements in validation functions.
• Merge the loops to initialize VALIDATE_xxx variables and to print enable/disable language debug messages.
• Add tests for these validation functions.
• Add test start message for all tests.

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[ferrarimarco]

@zkoppert Can you please have a look at this PR? It shouldn't have any visible side effect, but just in case :)

Thanks!

[zkoppert]

✅

[ferrarimarco]

Thanks for the review @zkoppert !