Make lvm volume group configurable

[pmtk]

Currently we use hardcoded myvg1 value, it would be nice to have it configurable, but the obstacle is that it's also hardcoded in the assets: https://github.com/openshift/microshift/blob/eb7c21fc035b806d3abe3c786e63516077442ae0/assets/optional/topolvm/03-topolvm.yaml#L78

[eslutsky]

we also need to configure the size correctly,currently it always 10Gi (which is too much for our testing env)

see spare-gb: 10 in
https://github.com/microshift-io/microshift/blob/main/src/topolvm/assets/03-topolvm.yaml#L78

the configuration should be reflected in the configmap:

data:
  lvmd.yaml: "socket-name: /run/topolvm/lvmd.sock\ndevice-classes: \n  - default: true\n    name: ssd\n    spare-gb: 10\n    volume-group: myvg1\n"

[randomlygeneratedname1]

My comment from the duplicate issue I created:

"...I used kustomize files in /etc/microshift/manifests.d/ to override the default config under /usr/... but it would be much better if one could use /etc/microshift/lvmd.yaml instead.

As a start maybe you could align the config in the default kustomize under /usr/... with what you have in /etc/microshift/lvmd.yaml.default (i.e. VG name as microshift both places instead of myvg1 in the kustomize yaml and microshift in the lvmd yaml)? And also add a comment in that file that it doesn't apply to bootc based installs? You could also make template kustomize files under /etc/microshift/manifests.d/ for users to override."