[DISCUSS] Cherry-pick PIP-469 to branch-4.2

[Yunze Xu]

Hi all,

PIP-469 [1] adds a metadata store based implementation of
TopicPoliciesService and does not change any existing implementation
or configuration. It would be helpful for users to try this new
implementation before 5.0, so I suggest cherry-picking it to
branch-4.2.

[1] https://github.com/apache/pulsar/pull/25707

Thanks,
Yunze