Make num-stages counter into an internal counter.

[robertwb]

This unbreaks tests that (arguably to brittly) reject extra counters.

---

Thank you for your contribution! Follow this checklist to help us incorporate your contribution quickly and easily:

• Choose reviewer(s) and mention them in a comment (R: @username).
• Format the pull request title like [BEAM-XXX] Fixes bug in ApproximateQuantiles, where you replace BEAM-XXX with the appropriate JIRA issue, if applicable. This will automatically link the pull request to the issue.
• Update CHANGES.md with noteworthy changes.
• If this contribution is large, please file an Apache Individual Contributor License Agreement.

See the Contributor Guide for more tips on how to make review process smoother.

ValidatesRunner compliance status (on master branch)

Lang	ULR	Dataflow	Flink	Samza	Spark	Twister2
Go	---					---
Java
Python	---					---
XLang						---

Examples testing status on various runners

Lang	ULR	Dataflow	Flink	Samza	Spark	Twister2
Go	---	---	---	---	---	---	---
Java	---		---	---	---	---	---
Python	---	---	---	---	---	---	---
XLang	---	---	---	---	---	---	---

Post-Commit SDK/Transform Integration Tests Status (on master branch)

Go	Java	Python

Pre-Commit Tests Status (on master branch)

---	Java	Python	Go	Website	Whitespace	Typescript
Non-portable
Portable	---			---	---	---

See .test-infra/jenkins/README for trigger phrase, status and link of all Jenkins jobs.

GitHub Actions Tests Status (on master branch)

See CI.md for more information about GitHub Actions CI.

[robertwb]

Follow-up from #16101

CC: @kileys

[codecov]

Codecov Report

Merging #16638 (7d3af58) into master (1351030) will increase coverage by 37.19%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master   #16638       +/-   ##
===========================================
+ Coverage   46.43%   83.63%   +37.19%     
===========================================
  Files         201      452      +251     
  Lines       19787    62095    +42308     
===========================================
+ Hits         9189    51931    +42742     
- Misses       9612    10164      +552     
+ Partials      986        0      -986     

Impacted Files	Coverage Δ
...eam/runners/portability/fn_api_runner/fn_runner.py	90.90% <ø> (ø)
sdks/go/pkg/beam/pardo.go
sdks/go/pkg/beam/partition.go
...pkg/beam/core/runtime/xlangx/expansionx/process.go
sdks/go/pkg/beam/core/runtime/genx/genx.go
sdks/go/pkg/beam/core/metrics/store.go
...ks/go/pkg/beam/core/runtime/harness/cache_hooks.go
sdks/go/pkg/beam/core/runtime/metricsx/urns.go
sdks/go/pkg/beam/core/runtime/graphx/serialize.go
sdks/go/pkg/beam/core/util/hooks/hooks.go
... and 644 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 1351030...7d3af58. Read the comment docs.

[robertwb]

Run Python PreCommit

[TheNeuralBit]

I guess internal: is a concept already defined somewhere?

[robertwb]

Yeah, there's some inconsistencies here with "user" counters requiring a name and namespace and "non-user" counters using the first component of the urn as a namespace and the rest as the name.

[robertwb]

The failing tests

apache_beam.transforms.create_test.CreateTest.test_create_uses_coder_for_pickling
apache_beam.transforms.combinefn_lifecycle_test.LocalCombineFnLifecycleTest_0.test_combine

look unrelated. Trying again.

[robertwb]

Run Python PreCommit

[robertwb]

(https://issues.apache.org/jira/browse/BEAM-13769)

[TheNeuralBit]

Run Python PreCommit

[ibzib]

I tried deflaking the Actions tests but it's unlikely to work since the rate of flakes is so high, there's no way to re-run individual actions, and the flakes can affect 8 different actions... I'm just going to merge this

[TheNeuralBit]

Thanks @ibzib, I think that the flakiness is actually resolved at HEAD, but for some reason github's /merge ref is pointing to an older commit cf79c26

[TheNeuralBit]

I suppose the merge ref is likely just created once when the PR is created and not updated.