feat(config): allow dev standin dbs to be semi-persistent through values.yaml

[corneliusroemer]

resolves #3254

preview URL: https://persistence.loculus.org

Need to revert from true to false before merging.

Summary

Allows not reloading the main and keycloak dbs for each commit in preview/dev deployments through values.yaml

Note that the database is 20+ minutes old while backend was replaced recently, that's what we can do now:

[theosanderson]

(if we do this [which sounds good] we probs want to do it for KC DB too?)

[corneliusroemer]

I was wondering how to name it, it seems a bit much to have booleans but then if we are happy with changing the config setting liberally, especially dev settings I'm happy not to worry too much.

Ideally, we'd back these dbs with a persistent volume claim but I don't know enough kubernetes to know how easy or hard that would be.

I thought about doing it for keycloak as well, just wanted to test it first for one.

[corneliusroemer]

The need to do this now arose because I was surprised that virus2's db got replaced after an update, so having the persistence option there through values yaml would be really good.

Persistence is a bit of a misnomer as db will get replaced under a few circumstances (eviction, change of kubernetes manifest params etc) but as it's a dev thing I'm not too worried.

[theosanderson]

Thanks