start to refactor persistence layer to prepare for direct path

[m-trieu]

Change classes that explicitly inject a MetricTrackingWindmillServerStub to take in a Function. This will give flexibility in later refactoring as we apply different ways to fetch the data without MetricTrackingWindmillServerStub. Add PersistentStateReadMetricsTracker, which is similar to MetricTrackingWindmillServerStub but allows callers to inject a GetDataStream (which is necessary for direct path since the calls need to be appropriately routed) and is streaming engine specific.

R: @scwhittle

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[m-trieu]

ready for another look @scwhittle

[m-trieu]

Run Java Precommit

[scwhittle]

Run Java PreCommit

[scwhittle]

Looks like this assert failed in test: https://github.com/apache/beam/blob/0bce6d7a834c521a3d3043ab9377fcd2f2e16f0a/runners/google-cloud-dataflow-java/worker/src/test/java/org/apache/beam/runners/dataflow/worker/StreamingDataflowWorkerTest.java#L3355

Could be flaky if doesn't wait enough to get commit or it could be an indication that the heartbeat response plumbing isn't working.

[m-trieu]

Looks like this assert failed in test:

https://github.com/apache/beam/blob/0bce6d7a834c521a3d3043ab9377fcd2f2e16f0a/runners/google-cloud-dataflow-java/worker/src/test/java/org/apache/beam/runners/dataflow/worker/StreamingDataflowWorkerTest.java#L3355

Could be flaky if doesn't wait enough to get commit or it could be an indication that the heartbeat response plumbing isn't working.

@scwhittle ran locally and it passed. looks we depend on sleep() in the test, and i wonder if that leads to flakiness in the GitHub actions environment?

    Map<Long, Windmill.WorkItemCommitRequest> commits =
        server.waitForAndGetCommitsWithTimeout(2, Duration.standardSeconds((5)));
    assertEquals(1, commits.size());

also kind of strange that we are waiting for 2 commits but are asserting that there is only 1 commit.

But looks like this is a flaky test failure

[scwhittle]

Run Java PreCommit

[scwhittle]

That test expects 1 commit but meant to wait for some extra time to make sure there were not 2. But it should do so perhaps with larger time limit for 1 and then shorter time limit to verify more don't show up.