forward port flaky test fix and add forecasting security tests

[kaituo]

Description

forward port flaky test fix in PR #1319 and add forecasting security tests.

Note 90,703 out of 93,529 changes are test data file change.

Check List

• New functionality includes testing.
• New functionality has been documented.
• API changes companion pull request created.
• Commits are signed per the DCO using --signoff.
• Public documentation issue/PR created.

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]

Codecov Report

Attention: Patch coverage is 90.41096% with 7 lines in your changes missing coverage. Please review.

Project coverage is 79.58%. Comparing base (062db14) to head (3d5b2d3).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
...g/opensearch/timeseries/ml/RealTimeInferencer.java	90.69%	3 Missing and 1 partial ⚠️
...va/org/opensearch/timeseries/task/TaskManager.java	0.00%	2 Missing ⚠️
...search/ad/transport/ADHCImputeTransportAction.java	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1329      +/-   ##
============================================
+ Coverage     79.32%   79.58%   +0.26%     
- Complexity     5593     5625      +32     
============================================
  Files           533      533              
  Lines         23363    23410      +47     
  Branches       2319     2323       +4     
============================================
+ Hits          18533    18632      +99     
+ Misses         3713     3667      -46     
+ Partials       1117     1111       -6     

Flag	Coverage Δ
plugin	79.58% <90.41%> (+0.26%)	⬆️

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

Files with missing lines	Coverage Δ
...ava/org/opensearch/ad/ml/ADRealTimeInferencer.java	100.00% <ø> (ø)
...search/forecast/ml/ForecastRealTimeInferencer.java	100.00% <ø> (ø)
...nsearch/forecast/rest/RestGetForecasterAction.java	82.60% <ø> (ø)
...nsport/SearchTopForecastResultTransportAction.java	2.47% <ø> (ø)
...ensearch/timeseries/TimeSeriesAnalyticsPlugin.java	99.36% <100.00%> (+<0.01%)	⬆️
...g/opensearch/timeseries/caching/PriorityCache.java	69.54% <100.00%> (ø)
...a/org/opensearch/timeseries/ml/ModelColdStart.java	80.20% <100.00%> (ø)
...ava/org/opensearch/timeseries/ml/ModelManager.java	90.00% <100.00%> (-1.43%)	⬇️
.../java/org/opensearch/timeseries/ml/ModelState.java	95.08% <100.00%> (ø)
...search/timeseries/settings/TimeSeriesSettings.java	94.73% <ø> (ø)
... and 5 more

... and 14 files with indirect coverage changes

[opensearch-trigger-bot]

The backport to 2.x failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Navigate to the root of your repository
cd $(git rev-parse --show-toplevel)
# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/anomaly-detection/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/anomaly-detection/backport-2.x
# Create a new branch
git switch --create backport/backport-1329-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 5704a169837e7302f44831e6a9de88387bc5611c
# Push it to GitHub
git push --set-upstream origin backport/backport-1329-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/anomaly-detection/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-1329-to-2.x.