feat(mc): Add dynamic filter options endpoint for model catalog

[syntaxsdev]

Description

Implements GET /api/model_catalog/v1alpha1/models/filter_options endpoint to dynamically provide
available filter options for the UI.

How Has This Been Tested?

• Added integration tests for repository layer (TestGetFilterableProperties)
• Added end-to-end tests for catalog layer (TestGetFilterOptions)
• Added HTTP endpoint tests (TestFindModelsFilterOptions)
• Existing tests pass

Merge criteria:

• All the commits have been signed-off (To pass the DCO check)

• The commits have meaningful messages
• Automated tests are provided as part of the PR for major new functionalities; testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• The developer has manually tested the changes and verified that the changes work.
• Code changes follow the kubeflow contribution guidelines.
• For first time contributors: Please reach out to the Reviewers to ensure all tests are being run, ensuring the label ok-to-test has been added to the PR.

If you have UI changes

• The developer has added tests or explained why testing cannot be added.
• Included any necessary screenshots or gifs if it was a UI change.
• Verify that UI/UX changes conform the UX guidelines for Kubeflow.

[google-oss-prow]

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[rareddy]

can rebase without pboyd's commit?

[mturley]

Any updates on this one @syntaxsdev ? I think it's the last big blocker we have on the UI side.