feat: add NamespacedStore CRD [multi-tenancy PR 8]

[binbin-li]

Description

What this PR does / why we need it:

This is the 8th PR for multi-tenancy support. Please review #1402 first. Check diff between PR 7 and PR 8 at: binbin-li#130

1. Created new CRD: NamespacedStore for namespaced Store resource and corresponding controller.
2. Updated implementation of ActiveStore so that it supports managing stores across namespaces.
3. Updated controlllers to reduce duplicate code between namespaced and clustered controllers.
4. Add unit tests.

Which issue(s) this PR fixes (optional, using fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when the PR gets merged):

Fixes #

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Helm Chart Change (any edit/addition/update that is necessary for changes merged to the main branch)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Please also list any relevant details for your test configuration

• Test A
• Test B

Checklist:

• Does the affected code have corresponding tests?
• Are the changes documented, not just with inline documentation, but also with conceptual documentation such as an overview of a new feature, or task-based documentation like a tutorial? Consider if this change should be announced on your project blog.
• Does this introduce breaking changes that would require an announcement or bumping the major version?
• Do all new files have appropriate license header?

Post Merge Requirements

• MAINTAINERS: manually trigger the "Publish Package" workflow after merging any PR that indicates Helm Chart Change

[codecov]

Codecov Report

Attention: Patch coverage is 77.27273% with 20 lines in your changes are missing coverage. Please review.

❗ No coverage uploaded for pull request base (dev@f006b88). Click here to learn what that means.

Files	Patch %	Lines
.../controllers/namespaceresource/store_controller.go	66.66%	11 Missing and 2 partials ⚠️
pkg/manager/manager.go	0.00%	7 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff           @@
##             dev    #1413   +/-   ##
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  Coverage       ?   66.81%           
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  Files          ?      116           
  Lines          ?     6029           
  Branches       ?        0           
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  Hits           ?     4028           
  Misses         ?     1618           
  Partials       ?      383           

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[akashsinghal]

Lgtm. Thanks!