Using the multi-version client in the CLI

When running fdbcli commands, we have to match the version of the CLI to the version of the server that we are talking to. This creates headaches when running different clusters at different versions, because you need to keep multiple versions of the CLI and select the right one based on the cluster. It's a particular pain point when killing processes during upgrades, because the CLI cannot connect to the database after the kill happens. Could we try to have the CLI go through the multi-version client so that we can use the latest version of the CLI regardless of which version of the server we're talking to?

Start by tracing how fdbcli establishes connections and where it could enter the multi-version client. Reproduce the version-mismatch and upgrade process-killing scenarios across differently versioned clusters. Done means the latest CLI can connect and run commands against supported server versions without maintaining separate CLI binaries.

Written by the indexing model from the issue text.