[BEAM-10505][BEAM-10530] Add truncate capability.

[boyuanzz]

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Post-Commit Tests Status (on master branch)

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

Pre-Commit Tests Status (on master branch)

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

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GitHub Actions Tests Status (on master branch)

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[boyuanzz]

r: @lukecwik

[boyuanzz]

Run Java PreCommit

[boyuanzz]

Run Python PreCommit

[codecov]

Codecov Report

Merging #12773 into master will increase coverage by 41.78%.
The diff coverage is 91.30%.

@@             Coverage Diff             @@
##           master   #12773       +/-   ##
===========================================
+ Coverage   40.23%   82.01%   +41.78%     
===========================================
  Files         455      457        +2     
  Lines       53726    54071      +345     
===========================================
+ Hits        21619    44349    +22730     
+ Misses      32107     9722    -22385     

Impacted Files	Coverage Δ
...s/python/apache_beam/io/gcp/bigquery_file_loads.py	90.59% <ø> (+67.23%)	⬆️
...hon/apache_beam/runners/direct/test_stream_impl.py	91.17% <55.55%> (+48.42%)	⬆️
sdks/python/apache_beam/transforms/core.py	88.53% <95.83%> (+50.25%)	⬆️
sdks/python/apache_beam/dataframe/frames.py	90.41% <100.00%> (+47.45%)	⬆️
sdks/python/apache_beam/portability/python_urns.py	100.00% <100.00%> (ø)
...hon/apache_beam/runners/worker/bundle_processor.py	94.05% <100.00%> (+65.37%)	⬆️
sdks/python/apache_beam/transforms/environments.py	83.87% <100.00%> (+31.44%)	⬆️
...he_beam/testing/benchmarks/nexmark/nexmark_util.py	0.00% <0.00%> (ø)
...eam/testing/benchmarks/nexmark/nexmark_launcher.py	0.00% <0.00%> (ø)
...he_beam/testing/benchmarks/nexmark/nexmark_perf.py	0.00% <0.00%> (ø)
... and 279 more

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[boyuanzz]

Kindly pinging : )