Issue 6861: fill repoIdentifier only for restic repo

[Lyndon-Li]

Fix #6861. Only Restic path requires repoIdentifier, so for non-restic path, set the repoIdentifier fields as empty in PVB and PVR and also remove the RepoIdentifier column in the get output of PVBs and PVRs

[codecov]

Codecov Report

Merging #6872 (10f2b79) into main (d3e5bb7) will decrease coverage by 0.01%.
Report is 3 commits behind head on main.
The diff coverage is 40.00%.

@@            Coverage Diff             @@
##             main    #6872      +/-   ##
==========================================
- Coverage   60.78%   60.77%   -0.01%     
==========================================
  Files         245      245              
  Lines       26255    26264       +9     
==========================================
+ Hits        15960    15963       +3     
- Misses       9164     9168       +4     
- Partials     1131     1133       +2     

Files	Coverage Δ
pkg/podvolume/backupper.go	85.94% <40.00%> (-1.00%)	⬇️
pkg/podvolume/restorer.go	90.00% <40.00%> (-1.40%)	⬇️

... and 1 file with indirect coverage changes

[Lyndon-Li]

@sseago @shubham-pampattiwar
Please help to review this PR. We want to remove the Repository ID column from the output of kubectl get podvolumebackup, since kopia is not the default path and it is always empty for kopia path.

[reasonerjt]

Let's double check with other maintainers and adopters about the break change to remove the repo ID when restic is chosen.

[shubham-pampattiwar]

@Lyndon-Li I think only the removal of printcolumn kubebuilder marker should be sufficient.