WIP: OnWindowExpiry, and OrderedListState WIP: DO NOT SUBMIT

[lostluck]

WIP: DO NOT SUBMIT

OnWindowExpiry:

• largely works, some tests are having hangs that aren't getting caught. Can't submit that yet. Likely related the other timer related hang test, or SDK side crashes.
• Otherwise seems feature complete. Better to implement other features blocking tests from executing to adding instability.

OrderedListState:

• the encoding wasn't clear until we saw that we certainly not getting the standard TimestampedValueCoder: https://github.com/apache/beam/blob/master/sdks/java/core/src/main/java/org/apache/beam/sdk/values/TimestampedValue.java#L108
• OrderedListState defines it's own. More compact, but was difficult to find. https://github.com/apache/beam/blob/master/sdks/java/harness/src/main/java/org/apache/beam/fn/harness/state/OrderedListUserState.java#L121
• Still TODO: Parsing out the individual values and sorting them correctly. TBD if we can cheekily re-use the bags instead of the VarInts, which would be nice.

WIP: DO NOT SUBMIT

---

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

• Mention the appropriate issue in your description (for example: addresses #123), if applicable. This will automatically add a link to the pull request in the issue. If you would like the issue to automatically close on merging the pull request, comment fixes #<ISSUE NUMBER> instead.
• 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.

To check the build health, please visit https://github.com/apache/beam/blob/master/.test-infra/BUILD_STATUS.md

GitHub Actions Tests Status (on master branch)

See CI.md for more information about GitHub Actions CI or the workflows README to see a list of phrases to trigger workflows.