[FLINK-9943] Support TaskManagerMetricQueryServicePaths msg in JobManager Actor

[chuanlei]

What is the purpose of the change

This pull request makes metric system be exposed to external akka client fully instead of only Jobmanager's metric*

Brief change log

• Add RequestTaskManagerMetricQueryServicePaths message in JobManager actor
• Add RequestTaskManagerMetricQueryServicePaths and TaskManagerMetricQueryServicePaths in JobMessages
• *Refactor TaskManagerMetricQueryServicePaths's requestTaskManagerMetricQueryServicePaths method *

Verifying this change

This change added tests and can be verified as follows:

• Manually verified the change by running a 4 node cluser with 2 JobManagers and 4 TaskManagers, WebRuntimeMonitor works correctly and external akka system can fetch metrics 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, Yarn/Mesos, 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)

[chuanlei]

@twalthr could you please have a look for this pr?

we think flink should expose its metrics directly via jobmanager so that we can develop 3rd party ui.

[chuanlei]

cc @zentol could you please have a look for this pr?

[tillrohrmann]

Thanks for opening this PR @chuanlei. Have you seen that Flink already exposes the metrics via REST. I think we should not expose internal components like the MetricQueryService because it would expose implementation details. Thus, I would vote to close this PR and the corresponding issue if the REST interface gives you what you need.

[isunjin]

could you also close the JIRA? @chuanlei