[improve][client] Implement GetLastMSgID for Reader

[liangyepianzhou]

Motivation

Implement the GetLastMSgID API for Reader.

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 yes was chosen, please highlight the changes

• Dependencies (does it add or upgrade a dependency): (yes / no)
• The public API: (yes / no)
• The schema: (yes / no / don't know)
• The default values of configurations: (yes / no)
• The wire protocol: (yes / no)

Documentation

• Does this pull request introduce a new feature? (yes / no)
• If yes, how is the feature documented? (not applicable / docs / GoDocs / not documented)
• If a feature is not applicable for documentation, explain why?
• If a feature is not documented yet in this PR, please create a followup issue for adding the documentation

[liangyepianzhou]

Leave a question: Do we have a plan to implement a multiple-topic reader?

[BewareMyPower]

Do we have a plan to implement a multiple-topic reader?

Not yet. But I think we can do that.

In addition, please add tests for the exposed API.

[liangyepianzhou]

@BewareMyPower Do you know which version of the go-client release will contain it?

[BewareMyPower]

Currently 0.11.0 is in release, so I think it's 0.12.0

[fud]

Just wondering when 0.12.0 would be released as we would love to use this feature?