[Python] Simulated call latency

[elliotcmorris]

Add "slow mode" to BAL #38 Add simulated call latency, configurable with the simulated_query_latency_ms settings variable. This allows testing of integrations that expect slow-to-return managers without having to test against a real manager, as well as providing a useful mechanism to explore scalability concerns.

Also adds new functional-behaviours test suite to hold non-business logic tests.

Testing is done via mocking time.sleep rather than testing timings, in order to try and avoid system timing instability issues.

co-authored @foundrytom

[elliotcmorris]

Made a fixup to address the linters now that they're running, added the max-similarity-lines thing mentioned in slack. https://github.com/OpenAssetIO/OpenAssetIO-Manager-BAL/pull/39/commits/e75263906b34dd5b9772e959d35332e583b119f6

edit: max similarity lines wasn't false positive, was an un-false positive, a true positive. Have remove the max-similarity-lines exception.