PWX-29422: Providing option to specify namespaces selector in migrati…

[pp511]

…on spec.

What type of PR is this?

feature

What this PR does / why we need it:
https://portworx.atlassian.net/browse/PWX-29422
Allow users to specify namespace selectors in migration spec.

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

Is a release note needed?:
Yes

• You can now provide namespace labels in MigrationSchedule spec to specify namespaces for migration.

Does this change need to be cherry-picked to a release branch?:
yes 23.5.0

Notes:

• I have added one function getMigrationNamespaces to get all unique namespaces for migration and referencing this list throughout our migration flow.

MigrationSchedule ->
spec:
 template:
   spec:
       namespaceSelectors:
         ns: migrate

Namespace ->
kind: Namespace
metadata:
 labels:
   kubernetes.io/metadata.name: mysql
   ns: migrate

• Triggered migration Jenkins job https://jenkins.pwx.dev.purestorage.com/job/Stork/view/Stork%2023.4-dev/job/23-4-dev-migration-k8s-1-24-0/473/console

[cnbu-jenkins]

Can one of the admins verify this patch?

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: +0.20 🎉

Comparison is base (cfb3d6d) 67.76% compared to head (abb3c3d) 67.96%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1395      +/-   ##
==========================================
+ Coverage   67.76%   67.96%   +0.20%     
==========================================
  Files          42       42              
  Lines        4889     4939      +50     
==========================================
+ Hits         3313     3357      +44     
- Misses       1242     1245       +3     
- Partials      334      337       +3     

see 2 files with indirect coverage changes

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