mappings traversal bug fix

[petardz]

Issue #, if available:

Description of changes:

Fixed few bugs with index mappings traversal which resulted in monitors not working.

CheckList:
[ ] Commits are signed per the DCO using --signoff

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[codecov-commenter]

Codecov Report

Merging #669 (f75899f) into main (0fb9dd0) will increase coverage by 0.22%.
The diff coverage is 80.64%.

@@             Coverage Diff              @@
##               main     #669      +/-   ##
============================================
+ Coverage     76.03%   76.26%   +0.22%     
  Complexity      116      116              
============================================
  Files           124      124              
  Lines          6606     6618      +12     
  Branches        980      982       +2     
============================================
+ Hits           5023     5047      +24     
+ Misses         1087     1071      -16     
- Partials        496      500       +4     

Impacted Files	Coverage Δ
...opensearch/alerting/util/DocLevelMonitorQueries.kt	80.35% <80.64%> (+0.35%)	⬆️
...pensearch/percolator/PercolatorFieldMapperExt.java	76.33% <0.00%> (+1.78%)	⬆️
.../kotlin/org/opensearch/alerting/util/IndexUtils.kt	72.91% <0.00%> (+2.08%)	⬆️
.../alerting/transport/TransportIndexMonitorAction.kt	62.57% <0.00%> (+2.63%)	⬆️

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[lezzago]

Can you add comments in the different logic flows of this function? It is kind of hard to follow what it is doing.

[petardz]

done

[opensearch-trigger-bot]

The backport to 2.x failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-2.x 2.x
# Navigate to the new working tree
cd .worktrees/backport-2.x
# Create a new branch
git switch --create backport/backport-669-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 0afcc4ae15519ab1eef6a8edfebb6b7e19fa78d4
# Push it to GitHub
git push --set-upstream origin backport/backport-669-to-2.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-669-to-2.x.

[opensearch-trigger-bot]

The backport to 2.4 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-2.4 2.4
# Navigate to the new working tree
cd .worktrees/backport-2.4
# Create a new branch
git switch --create backport/backport-669-to-2.4
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 0afcc4ae15519ab1eef6a8edfebb6b7e19fa78d4
# Push it to GitHub
git push --set-upstream origin backport/backport-669-to-2.4
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.4

Then, create a pull request where the base branch is 2.4 and the compare/head branch is backport/backport-669-to-2.4.