[BEAM-3900] Improvements in Metrics translation, composite transforms, tests and win. API

[VaclavPlajt]

List of improvements:

• Larger portfolio of Euphoria test suite was enabled.
• Translation of Euphoria Accumulators to Beam Metrics was added.
• Euphoria windowing API adapted to Beam windowing.
• Operator's API now consumes type hints to allow set coders automatically.
• Composite transforms can be defined through Euphoria API.
• Cleanup: Flipping tests fixed, Euphoria executor concept removed, two project modules where merged
  R: @jbonofre

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Post-Commit Tests Status (on master branch)

Lang	SDK	Apex	Dataflow	Flink	Gearpump	Spark
Go		---	---	---	---	---
Java
Python		---		---	---	---

[kennknowles]

We have turned on autoformatting of the codebase, which causes small conflicts across the board. You can probably safely rebase and just keep your changes. Like this:

$ git rebase
... see some conflicts
$ git diff
... confirmed that the conflicts are just autoformatting
... so we can just keep our changes are do our own autoformat
$ git checkout --theirs --
$ git add -u
$ git rebase --continue
$ ./gradlew spotlessJavaApply

Please ping me if you run into any difficulty.

[VaclavPlajt]

please retest this

[mareksimunek]

Run Java PreCommit

[akedin]

Is this PR in progress or should we close it as stale?

[VaclavPlajt]

Hi,
this PR definitely stall. Thanks for your comment.