[FLINK-26723][runtime]fix the error message thrown by SourceCoordinatorContext

[zoucao]

What is the purpose of the change

fix the error message thrown by SourceCoordinatorContext

Brief change log

fix the error message SourceCoordinatorContext
provide more message for test in SourceCoordinatorContextTest

Verifying this change

Please make sure both new and modified tests in this PR follows the conventions defined in our code quality guide: https://flink.apache.org/contributing/code-style-and-quality-common.html#testing

(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 (100MB)
• Extended integration test for recovery after master (JobManager) failure
• Added test that validates that TaskInfo is transferred only once across recoveries
• Manually verified the change by running a 4 node cluster with 2 JobManagers and 4 TaskManagers, a stateful streaming program, and killing one JobManager and two TaskManagers during the execution, verifying that recovery happens correctly.

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

• Dependencies (does it add or upgrade a dependency): (yes / no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (yes / no)
• The serializers: (yes / no / don't know)
• The runtime per-record code paths (performance sensitive): (yes / no / don't know)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (yes / no / don't know)
• The S3 file system connector: (yes / no / don't know)

Documentation

• Does this pull request introduce a new feature? (yes / no)
• If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented)

[zoucao]

@flinkbot run azure

[zoucao]

Gentle ping @becketqin, could you help me to review this pr in your spare time ?

[flinkbot]

CI report:

• 627769a Azure: FAILURE

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot run azure re-run the last Azure build

[zoucao]

@flinkbot run azure

[becketqin]

LGTM. The CI failure should be irrelevant to this PR.

[becketqin]

Merged to master: da79677
Cherry-picked to

• release-1.15: e3992ab
• release-1.14: 36136bc