Bump Khepri from 0.13.0 to 0.14.0

[dumbbell]

Release notes: https://github.com/rabbitmq/khepri/releases/tag/v0.14.0

While here, bump khepri_mnesia_migration from 0.4.0 to 0.5.0 as well.

[dumbbell]

Upgrading Khepri is less straightforward than expected, because of the bump of the Khepri state machine version. This highlights two problems during mixed version testing:

1. A state machine that runs an older state machine version can’t apply commands. This leads to commands timing out.
2. Local Khepri function references may be invalid on a remote Khepri instance because modules are not the same.

The former is not a bug. This is a behavior inherent to Raft that we need to take into account in the testsuites.

The latter is a known limitation that we started to discuss in rabbitmq/khepri#238 and rabbitmq/khepri#242. We are still studying the issue, nothing is implemented as of this writing.

[the-mikedavis]

Force-push was a rebase

[the-mikedavis]

Superseded by #11668 and #11663