feat: add policy crd and controller

[binbin-li]

Description

What this PR does / why we need it:

1. Add Policy CRD to support switching between config/rego policies in runtime.
2. Add Policy controller that manipulate the active policy in Ratify. There would be at most 1 policy existing in Ratify as Ratify cannot apply multiple policies. That means when users apply a new CR, the old CR would be removed from cluster. And if there are no CR added, config policy will be the default one.
3. Refactor executor to remove duplicate code, there is no actual logic change.
4. Add a new API(GetPolicyType) to PolicyProvider interface to distinguish between policy enforcers without featureFlag.
5. Remove PassthroughMode from featureFlag, add it as a field under RegoPolicyConfig
6. Remove Use_Rego_Policy from featureFlag, but add it as a regular chart value.
7. Update docs.

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 #936

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

Updated e2e tests.
Manual test:

1. Deploy ratify with config policy.
2. Apply Rego Policy CR.
3. Apply Config Policy CR.
4. Apply Rego Policy CR.
5. Delete Rego Policy CR.

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

[susanshi]

just left a comment a about small typo, otherwise looks good. thanks!