Fix 'getName is not a function' issue for query manager

[mengweieric]

Description

Fix 'getName is not a function' issue

Issues Resolved

#1042

Check List

• New functionality includes testing.
  • All tests pass, including unit test, integration test and doctest
• New functionality has been documented.
  • New functionality has javadoc added
  • New functionality has user manual doc added
• Commits are signed per the DCO using --signoff

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[codecov-commenter]

Codecov Report

Merging #1160 (721eb3e) into main (7930865) will decrease coverage by 0.01%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##               main    #1160      +/-   ##
============================================
- Coverage     53.72%   53.70%   -0.02%     
  Complexity      291      291              
============================================
  Files           279      279              
  Lines          9486     9488       +2     
  Branches       2242     2244       +2     
============================================
  Hits           5096     5096              
- Misses         4220     4222       +2     
  Partials        170      170              

Flag	Coverage Δ
dashboards-observability	47.86% <0.00%> (-0.02%)	⬇️
opensearch-observability	71.87% <ø> (ø)

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

Impacted Files	Coverage Δ
...mon/query_manager/ast/builder/stats_ast_builder.ts	0.00% <0.00%> (ø)
.../common/query_manager/ast/builder/stats_builder.ts	0.00% <0.00%> (ø)

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