Add stream context and window trigger

[dai-chen]

Description

As another main component for stream data windowing, this PR adds Window Trigger along with Stream Context.

Stream Context

A stream context holds useful context information for all stream processing components. It’s also easy to store and restore between executions by put all state in one place.

Window Trigger

A window trigger determines whether to trigger window state output (a window pane). Common trigger implementation includes:

• After Watermark: trigger if the window is below watermark.
• Count: trigger based on a counter. A special case is per-event trigger for materialized view semantics.
• Time: trigger when its time comes.

Note that window trigger is easy to be confused with watermark. Watermark is the way to reason about the completeness of window state. Window trigger upon user configuration can decide to trigger output no matter the window state is complete or not.

Issues Resolved

#951

Check List

• New functionality includes testing.
  • All tests pass, including unit test, integration test and doctest
• New functionality has been documented.
  • New functionality has javadoc added
  • New functionality has user manual doc added
• Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[codecov-commenter]

Codecov Report

Merging #958 (f3db6ad) into feature/maximus-m1 (91baab1) will decrease coverage by 35.19%.
The diff coverage is n/a.

@@                    Coverage Diff                    @@
##             feature/maximus-m1     #958       +/-   ##
=========================================================
- Coverage                 97.96%   62.76%   -35.20%     
=========================================================
  Files                       303       10      -293     
  Lines                      7805      658     -7147     
  Branches                    504      119      -385     
=========================================================
- Hits                       7646      413     -7233     
- Misses                      158      192       +34     
- Partials                      1       53       +52     

Flag	Coverage Δ
query-workbench	62.76% <ø> (?)
sql-engine	?

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Impacted Files	Coverage Δ
...c/main/java/org/opensearch/sql/ppl/PPLService.java
...c/main/java/org/opensearch/sql/expression/DSL.java
.../opensearch/sql/planner/logical/LogicalDedupe.java
...rch/planner/logical/rule/MergeSortAndRelation.java
...org/opensearch/sql/analysis/QualifierAnalyzer.java
.../opensearch/sql/planner/logical/LogicalFilter.java
...pensearch/sql/opensearch/mapping/IndexMapping.java
...ql/analysis/model/CatalogSchemaIdentifierName.java
.../org/opensearch/sql/sql/parser/AstSortBuilder.java
...ion/operator/predicate/UnaryPredicateOperator.java
... and 303 more

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[penghuo]

Thanks.