[FLINK-18355][tests] Simplify tests of SlotPoolImpl

[Thesharing]

What is the purpose of the change

Tests of SlotPoolImpl, including SlotPoolImplTest and SlotPoolInteractionsTest, are somehow unnecessarily complicated in the code involvement. E.g. SchedulerImp built on top of SlotPoolImpl is used to allocate slots from SlotPoolImpl, which can be simplified by directly invoke slot allocation on SlotPoolImpl.

Besides that, there are quite some duplications between tests classes of SlotPoolImpl, this further includes SlotPoolPendingRequestFailureTest, SlotPoolRequestCompletionTest and SlotPoolBatchSlotRequestTest.

Brief change log

• Use SlotPoolBuilder and SlotPoolUtils to refactor test cases related to SlotPoolImpl
• Remove the usages of SchedulerImp for slotpool testing
• Other possible simplifications

Verifying this change

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

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/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)

[flinkbot]

Thanks a lot for your contribution to the Apache Flink project. I'm the @flinkbot. I help the community
to review your pull request. We will use this comment to track the progress of the review.

Automated Checks

Last check on commit e9db5e6 (Fri Jul 17 07:44:33 UTC 2020)

Warnings:

• No documentation files were touched! Remember to keep the Flink docs up to date!
• Invalid pull request title: No valid Jira ID provided

_{Mention the bot in a comment to re-run the automated checks.}

Review Progress

• ❓ 1. The [description] looks good.
• ❓ 2. There is [consensus] that the contribution should go into to Flink.
• ❓ 3. Needs [attention] from.
• ❓ 4. The change fits into the overall [architecture].
• ❓ 5. Overall code [quality] is good.

Please see the Pull Request Review Guide for a full explanation of the review process.

The Bot is tracking the review progress through labels. Labels are applied according to the order of the review items. For consensus, approval by a Flink committer of PMC member is required

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot approve description to approve one or more aspects (aspects: description, consensus, architecture and quality)
• @flinkbot approve all to approve all aspects
• @flinkbot approve-until architecture to approve everything until architecture
• @flinkbot attention @username1 [@username2 ..] to require somebody's attention
• @flinkbot disapprove architecture to remove an approval you gave earlier

[flinkbot]

CI report:

• da7fb96 UNKNOWN
• bce6761 UNKNOWN
• cb4298b UNKNOWN
• d489b53 UNKNOWN
• 0ff06bb Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

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

[zhuzhurk]

Thanks for opening this PR @Thesharing .
I left a few comments for the first commit. Will continue reviewing the other commits.

[Thesharing]

Really appreciate for your reviews. I've already made fixes according to your comments and submitted a fix-up commit.

[Thesharing]

I've already pushed a fix-up commit about "Refactor SlotPoolImplTest with SlotPoolTestBase".

[Thesharing]

Thanks for your review. It's really nice of you. I've fixed some of them according to your comments.

[Thesharing]

Thanks for your review. I've already got it fixed according to your comments.

[Thesharing]

Thanks for your review. I've get it fixed according to your comments and force push the newest codes.

[Thesharing]

Sorry for being so careless. I'll be more careful next time. Thank you for your review.

[Thesharing]

@flinkbot run azure

[Thesharing]

@flinkbot run travis

[Thesharing]

I've already rebased my commits on the latest master branch. Would you please take a look, @zhuzhurk ?

[zhuzhurk]

LGTM. Merging since AZP gives green.