[Task] Development and CI runs should use h2:file mode by default

[andrewazores]

h2:file is more representative of a real Cryostat deployment than h2:mem is, since persistence would generally be wanted for the JMX credentials keyring at least and also for the discovery database (especially custom targets). The Operator will deploy in h2:file mode when there is an associated PVC and storage space to put the file on:

cryostatio/cryostat-operator#451

h2:mem should remain a configurable option and should also be easily selectable for development since it may also have its own uses for "ephemeral" Cryostat instances.