[v3-0-test] Allow Remote logging providers to load connections from the API Server (#53719)

[github-actions]

Often remote logging is down using automatic instance profiles, but not
always. If you tried to configure a logger by a connection defined in the
metadata DB it would have not worked (it either caused the supervise job to
fail early, or to just behave as if the connection didn't exist, depending on
the hook's behaviour)

Unfortunately, the way of knowing what the default connection ID various hooks
use is not easily discoverable, at least not easily from the outside (we can't
look at remote.hook as for most log providers that would try to load the
connection, failing in the way we are trying to fix) so I updated the log
config module to keep track of what the default conn id is for the modern log
providers.

Once we have the connection ID we know (or at least have a good idea that
we've got the right one) we then pre-emptively check the secrets backends for
it, if not found there load it from the API server, and then either way. if we
find a connection we put it in the env variable so that it is available.

The reason we use this approach, is that are running in the supervisor process
itself, so SUPERVISOR_COMMS is not and cannot be set yet.
(cherry picked from commit e4fb686)

Co-authored-by: Ash Berlin-Taylor [email protected]