enhance parsing model response function for more edge cases

[ylwu-amzn]

Description

Enhance parsing model response function for more edge cases

1. Model output is invalid json
2. Model output has no valid field.

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

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]

Codecov Report

Attention: 12 lines in your changes are missing coverage. Please review.

Comparison is base (3b162db) 81.86% compared to head (cf94a99) 81.86%.
Report is 2 commits behind head on main.

Files	Patch %	Lines
...nsearch/ml/engine/algorithms/agent/AgentUtils.java	90.09%	3 Missing and 7 partials ⚠️
.../ml/engine/algorithms/agent/MLChatAgentRunner.java	92.30%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2122      +/-   ##
============================================
- Coverage     81.86%   81.86%   -0.01%     
- Complexity     5644     5657      +13     
============================================
  Files           543      543              
  Lines         22790    22843      +53     
  Branches       2333     2347      +14     
============================================
+ Hits          18658    18701      +43     
- Misses         3195     3203       +8     
- Partials        937      939       +2     

Flag	Coverage Δ
ml-commons	81.86% <90.69%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.