As agreed in the PTG [1], deprecate the prometheus datasource in favor
of aetos, to be removed in a future release.
The change marks the prometheus datasource as deprecate, changes the
default value of the watcher_datasources config option (replacing
prometheus by aetos), updates both aetos and prometheus datasources
documentation and adds a migration guide detailing how to migrate a
Watcher using prometheus to use aetos.
[1] https://etherpad.opendev.org/p/watcher-2026.1-ptg#L207
Assisted-By: claude-code (clade-sonnet-4.5)
Change-Id: Id93a5e6a02dab40390eff744b474acd08ca85fa5
Signed-off-by: jgilaber <jgilaber@redhat.com>
9132e604b6