Refine backend / frontend version check

[confluence]

This idea came out of the discussion surrounding #1281. The strictness of the version check should be configurable with a preference (options: exact match, minor version, major version, disabled), with a default to be discussed (perhaps configurable with a build option?).

This would allow us to use minor and major bumps in the protobuf repo to distinguish between changes that affect specific features and changes that affect the whole application, and to couple public-facing packaged components tightly while mixing and matching them internally as broadly as we want for testing purposes.