Support disabling topic policies and transaction in namespace level

### Search before reporting

- [x] I searched in the [issues](https://github.com/apache/pulsar/issues) and found nothing similar.

### Motivation

There are many issues with the current topic policies and transaction, especially topic policies are enabled by default currently.

https://github.com/apache/pulsar/issues?q=is%3Aissue%20state%3Aopen%20topic%20policies

Each namespace has a `__change_events` topic and `__transaction_buffer_snapshot` topic. It will have much pressure on the compaction service and the system topic based solution has many bugs.

In many cases, users don't need a topic level policy. For example, KoP creates some topics in `public/__kafka` namespace as the key-value store. I've encountered many incidents caused by loading `__change_events` or `__transaction_buffer_snapshot`.

### Solution

Add some fields to namespace policies to disable topic policies and transaction. I will prepare a PIP for it.

### Alternatives

_No response_

### Anything else?

_No response_

### Are you willing to submit a PR?

- [x] I'm willing to submit a PR!