[improve][broker] PIP-360 Add admin API to display Schema metadata

[rdhabalia]

PIP-360: #22913

Motivation

Schema is one of the important part of the topic because it also plays important part in topic availability and required to successfully load the topic, and if schema initialization failure is causing issue in topic loading then it is very important to get schema metadata information to understand schema related issues and perform appropriate actions to mitigate that issue to successfully load the topic and make it available for users. Therefore, similar to ledger metadata and managed-ledger metadata, Pulsar should have API to show schema metadata and related ledger info which can be used by tools or users to perform appropriate actions during topic availability issues or any other troubleshooting.

Modifications

Adding admin API and cli to read schema metadata.

Verifying this change

• Make sure that the change passes the CI checks.

(Please pick either of the following options)

This change is a trivial rework / code cleanup without any test coverage.

(or)

This change is already covered by existing tests, such as (please describe tests).

(or)

This change added tests and can be verified as follows:

(example:)

• Added integration tests for end-to-end deployment with large payloads (10MB)
• Extended integration test for recovery after broker failure

Does this pull request potentially affect one of the following parts:

If the box was checked, please highlight the changes

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

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