[Go SDK] Encode INT16 row fields as big endian to match Java and Python

[Eliaaazzz]

Fixes #40151. Part of #39684.

The reflection based row coder encoded int16 and uint16 struct fields with the varint encoding. Java (BigEndianShortCoder) and Python (BigEndianShortCoder) encode the INT16 schema type as 2 big endian bytes, so rows with such fields could not be exchanged with the other SDKs. The beam:logical_type:timestamp:v1 cases in standard_coders.yaml depend on this encoding for precisions below 5.

Changes:

• Add coder.EncodeInt16, DecodeInt16, EncodeUint16 and DecodeUint16.
• The row encoder and decoder use them for int16 and uint16 fields. uint16 is stored as an INT16 schema field.
• Byte level test against the Java and Python encoding.
• CHANGES.md breaking change note: this is an update incompatible change for streaming pipelines that use rows with int16 or uint16 fields.

This is the first PR of a series for #39684 (Go SDK portable logical types).

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[github-actions]

Checks are failing. Will not request review until checks are succeeding. If you'd like to override that behavior, comment assign set of reviewers

[Abacn]

Int8 (BYTE) likely has similar inconsistency. Consider a same fix here, or could be a follow up

edit: It's fine: BYTE is backed by uint8. See https://github.com/Eliaaazzz/beam/blob/15745eb513417942b6cfe563961edb508804bd8a/sdks/go/pkg/beam/core/runtime/graphx/schema/schema.go#L658

[github-actions]

Assigning reviewers:

R: @shunping for label go.

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[github-actions]

Reminder, please take a look at this pr: @shunping

[jrmccluskey]

@Eliaaazzz please consider iterating on this PR soon, as you have a number of code changes in a chain that we'd like to review and get in!

[Eliaaazzz]

@jrmccluskey Thanks for the reminder, and sorry for the delay. Yi's CHANGES.md comment is addressed in b9b7d27, so this one is ready for another look. #40153 and #40154 build on it and are ready for review as well.

[codecov]

Codecov Report

❌ Patch coverage is 82.22222% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.51%. Comparing base (2bf8ba5) to head (b9b7d27).
⚠️ Report is 211 commits behind head on master.

Files with missing lines	Patch %	Lines
sdks/go/pkg/beam/core/graph/coder/int.go	76.47%	2 Missing and 2 partials ⚠️
sdks/go/pkg/beam/core/graph/coder/row_decoder.go	77.77%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #40152      +/-   ##
============================================
+ Coverage     55.09%   56.51%   +1.42%     
  Complexity     1722     1722              
============================================
  Files          1076     1076              
  Lines        171812   160948   -10864     
  Branches       1262     1262              
============================================
- Hits          94658    90961    -3697     
+ Misses        74880    67693    -7187     
- Partials       2274     2294      +20     

Flag	Coverage Δ
go	28.39% <82.22%> (-0.75%)	⬇️

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[jrmccluskey]

LGTM, thank you!