Add version to DatabaseRequires interface

[carlcsaposs-canonical]

Database requirer should specify which version of the database it needs (e.g. mysql version, not charm revision) so that the provider knows if it's safe to upgrade the database version

Requires changes to https://github.com/canonical/charm-relation-interfaces

[github-actions]

https://warthogs.atlassian.net/browse/DPE-1923

[taurus-forever]

My $0.05: mysql charm need to know mysql-router version to block "juju refresh mysql" if router is not-yet upgraded, etc.
So, database requirer (mysql-router) should specify his (mysql-router) version when relating to database provider (mysql-server).

Most probably, there are more use-cases for mysql to know router version (charm revision, router snap/deb version, interface version we are related thorugh, profile version used, ..., ....).