[fix] [broker] Make ManagedLedger and ManagedCursor suit the custom plugin.

[horizonzy]

Motivation

Now, we force cast class at the out side of module managed-ledger, if some users want to use the custom ManagedLedger, it will throw ClassCastException.
So we should only use the interface level out side of module managed-ledger.

Modifications

Extract some methods to the ManagedLedger interface when we need.

Verifying this change

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(Please pick either of the following options)

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

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

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This change added tests and can be verified as follows:

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• 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

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