Avoid pebble injection if OCI ships pebble

[Alex Lutay]

Hi,

Data Platfrom team has faced the following situation:
 * Pebble has implemented new feature to shutdown DB safely: https://github.com/canonical/pebble/pull/190
 * Juju 2.9.44 and Charm have migrated on new Pebble: https://github.com/canonical/mysql-k8s-operator/pull/258
 * User noticed degradation on 2.9.42: https://warthogs.atlassian.net/browse/DPE-2396

Proposal: juju will stop injecting pebble into OCI is pebble is available there already.
We can ship latest (compatible with charm.py) version into our OCI => users will be able to run charm using old Juju 2.9.42.

Tnx!

P.S. The long internal discussion is here: https://chat.charmhub.io/charmhub/pl/hbwsck5jxb8q8gzig9mnhoc3yw

[Jon Seager (jnsgruk)]

I don't think we can agree to this - we could run into some pretty hairy problems if Juju is expecting certain features to be available in the Pebble, but the version shipped in the container doesn't support them.

This feels like a pretty easy way for us to introduce uncertainty and instability.

[Joseph Phillips (manadart)]

I've marked this as RFE, but I'd suggest we are unlikely to take this on, at least in the short term.

I'm aware of increased rigour around Pebble releases and adoption in Juju that should guard against regressions/bugs.