[CHORE] Review gherkin suite and test-harness for missing test coverage

Our testbed covers all our operators, and some behavior around connection and re-connection. The goal of this issue is to identify and enumerate shortcomings in this suite which can be tackled in other issue(s).

For example (not sure if any of these are ACTUALLY missing or not):

• missing edge cases for custom operations (fraction, sem_ver, etc)
• missing tests for built-in JsonLogic operators
• missing test cases for provider misconfiguration
• missing test cases for error scenarios

Tips:

• Review https://github.com/open-feature/flagd-testbed/tree/main/flags, which contains all the flags in the testbed. Make sure the flags here exercise all possible operators and their key use-cases
• Review https://github.com/open-feature/flagd-testbed/tree/main/gherkin, which contains the tests/assertions, and make sure all the assertions are robust and all functionality is represented

Start by reviewing the flagd-testbed flags directory, then inspect its gherkin directory and assertions. Compare the covered operators, connection and reconnection behavior, provider configuration, and error scenarios against the stated examples. Done means producing an enumeration of missing or weak coverage that can be addressed in follow-up issues.