[Xray] Add option to enable/disable PDB

[nu12]

Hi there,

My client has been using XRay for years without a PDB and everything went fine, but a recent change was made and now the deployment creates a PDB that blocks nightly node operations. This is the change:

(3cd3f85)

Since the existence of xray.minAvailable is the only variable controlling the PDB creation and that the change was made to the default values file, I can no longer skip the PDB creation, I can only configure it to zero, which is not very convenient.

Could we have something like xray.pdb.enabled and xray.pdb.minAvailable instead to have better control over it? I'd like to be able to not have this PDB at all.

On a side note, there is no mention of the new default PDB in the Changelog, which in itself is an issue for people doing upgrades between versions.

Thank you