PB-4245 :: Restrict backup of "kube-system" ns

[vikasit12]

• Restrict backup of "kube-system" in case of all namespaces i.e. *
• Restrict backup of "kube-system" in case of label-selector
• Allow backup of "kube-system" in case API is specifically passing it i.e. namsespace=kube-system in API call

What type of PR is this?

feature

What this PR does / why we need it:
This PR restricts kube-system ns backup in below scenarios.

• Restrict backup of "kube-system" in case of all namespaces i.e. *
• Restrict backup of "kube-system" in case of label-selector

Does this PR change a user-facing CRD or CLI?:

no

Is a release note needed?:

yes

Issue: #PB-4245
User Impact: User will not be able to backup kube-system namespace if tried with label-selector or all namespace
Resolution: If user wants to backup kube-system namespace the one needs to pass it specifically as namsespace=kube-system in API calls

Does this change need to be cherry-picked to a release branch?:

yes, 23.9

Testing Screenshot

Before fix

After Fix

[cnbu-jenkins]

Can one of the admins verify this patch?