add support for opensearch 2.19

[Jakob3xD]

Description

Adds the newly added fields. IDK if all the types are correct, as they are not documented in the open API spec.

Issues Resolved

Closes #668

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 62.66%. Comparing base (06a6dc8) to head (07f24fd).
Report is 83 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #669      +/-   ##
==========================================
+ Coverage   57.29%   62.66%   +5.37%     
==========================================
  Files         315      376      +61     
  Lines        9823    11133    +1310     
==========================================
+ Hits         5628     6977    +1349     
+ Misses       2902     2876      -26     
+ Partials     1293     1280      -13     

Flag	Coverage Δ
integration	54.79% <ø> (+3.95%)	⬆️
unit	15.48% <ø> (+2.63%)	⬆️

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Files with missing lines	Coverage Δ
opensearchapi/api_cluster-stats.go	100.00% <ø> (ø)
opensearchapi/api_indices-stats.go	83.33% <ø> (ø)
opensearchapi/api_nodes-info.go	100.00% <ø> (ø)
opensearchapi/api_nodes-stats.go	100.00% <ø> (ø)

... and 31 files with indirect coverage changes