funcx-endpoint should report an error if the service version is unsupported

Currently, if a funcx-endpoint is launched against an older funcx-web-service deployment a random error will be thrown. We should instead be checking the version and reporting a cleaner error message to the user. Secondly, we should update the API version numbers when there are breaking changes, such as the ones we have in the forwarder_rearch effort.

Start at the funcx-endpoint path that connects to an older funcx-web-service deployment, then inspect how the service version and API version are currently represented. Done means unsupported versions produce a clean user-facing error and breaking API changes, including the forwarder_rearch changes, use updated version numbers; no specific files or tests are named.

Written by the indexing model from the issue text.