separate get Trace actions into a new rest API

[Zhangxunmt]

Description

Only return final results in the "List Conversation" API. Add a new API of "Get Trace" to return only traces for an interaction.

Issues Resolved

[List any issues this PR will resolve]

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff

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[ylwu-amzn]

Trace is only for conversation agent, to make it general, maybe build a general search API for interaction data ?

[Zhangxunmt]

The general search API already exists. This "get trace" is only meant for the conversation agent to let FE use. The "list interaction" will only return interactions that have "null" trace_number (final response). In other agents, the "list interactions" API still works to list all interactions because the "trace_number" is null since it's only used in the conversational context.

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (becfbe0) 66.46% compared to head (c0bfaea) 66.42%.

Files	Patch %	Lines
.../opensearch/ml/rest/RestMemoryGetTracesAction.java	60.00%	2 Missing ⚠️

Additional details and impacted files

@@                        Coverage Diff                        @@
##             feature/agent_framework_dev    #1672      +/-   ##
=================================================================
- Coverage                          66.46%   66.42%   -0.04%     
- Complexity                          2520     2521       +1     
=================================================================
  Files                                231      232       +1     
  Lines                              12554    12560       +6     
  Branches                            1268     1268              
=================================================================
- Hits                                8344     8343       -1     
- Misses                              3657     3663       +6     
- Partials                             553      554       +1     

Flag	Coverage Δ
ml-commons	66.42% <66.66%> (-0.04%)	⬇️

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