opensearchapi: add MaxScore field to ScrollGetResp

[Jakob3xD]

Description

Add MaxScore field to ScrollGetResp

Issues Resolved

https://github.com/opensearch-project/opensearch-go/actions/runs/10579861232/job/29313341627?pr=606#step:7:993

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.99%. Comparing base (06a6dc8) to head (35591ee).
Report is 62 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #607       +/-   ##
===========================================
+ Coverage   57.29%   67.99%   +10.70%     
===========================================
  Files         315      376       +61     
  Lines        9823     8862      -961     
===========================================
+ Hits         5628     6026      +398     
+ Misses       2902     1555     -1347     
+ Partials     1293     1281       -12     

Flag	Coverage Δ
integration	60.35% <ø> (+9.51%)	⬆️
unit	15.37% <ø> (+2.53%)	⬆️

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Files	Coverage Δ
opensearchapi/api_scroll-get.go	100.00% <ø> (ø)

... and 274 files with indirect coverage changes