Handle monitor or monitor index not found during detector deletion

[eirsep]

Description

Handle monitor or monitor index(.opendistro-alerting-config) not found during detector deletion to proceed with detector deletion.
But if there are other errors thrown from monitor deletion then we log it and fail the request

Issues Resolved

#378

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-commenter]

Codecov Report

Merging #384 (2f4d975) into main (12e4a56) will decrease coverage by 0.87%.
The diff coverage is 2.60%.

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@@             Coverage Diff              @@
##               main     #384      +/-   ##
============================================
- Coverage     36.53%   35.66%   -0.87%     
  Complexity      887      887              
============================================
  Files           185      186       +1     
  Lines          7098     7285     +187     
  Branches        860      885      +25     
============================================
+ Hits           2593     2598       +5     
- Misses         4268     4450     +182     
  Partials        237      237              

Impacted Files	Coverage Δ
...rch/securityanalytics/SecurityAnalyticsPlugin.java	0.00% <0.00%> (ø)
...rch/securityanalytics/action/AckAlertsRequest.java	75.00% <ø> (ø)
...ch/securityanalytics/action/AckAlertsResponse.java	77.27% <ø> (ø)
.../opensearch/securityanalytics/action/AlertDto.java	50.45% <ø> (ø)
...tyanalytics/action/CreateIndexMappingsRequest.java	46.93% <ø> (ø)
...curityanalytics/action/DeleteDetectorResponse.java	0.00% <ø> (ø)
...h/securityanalytics/action/DeleteRuleResponse.java	0.00% <ø> (ø)
...pensearch/securityanalytics/action/FindingDto.java	37.20% <ø> (ø)
...ch/securityanalytics/action/GetAlertsResponse.java	35.29% <ø> (ø)
...analytics/action/GetAllRuleCategoriesResponse.java	0.00% <ø> (ø)
... and 55 more

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[opensearch-trigger-bot]

The backport to 2.5 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-2.5 2.5
# Navigate to the new working tree
cd .worktrees/backport-2.5
# Create a new branch
git switch --create backport/backport-384-to-2.5
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 6271399c381a33364927e8147b6d6e3bc3f583cc
# Push it to GitHub
git push --set-upstream origin backport/backport-384-to-2.5
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.5

Then, create a pull request where the base branch is 2.5 and the compare/head branch is backport/backport-384-to-2.5.