[Backport 2.x] Filter datasource encryption master key from cluster settings GET API

[opensearch-trigger-bot]

Backport a8ecd2f from #1825

[codecov]

Codecov Report

Merging #1828 (78773fc) into 2.x (2144ddd) will increase coverage by 0.08%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##                2.x    #1828      +/-   ##
============================================
+ Coverage     97.35%   97.44%   +0.08%     
- Complexity     4443     4622     +179     
============================================
  Files           388      388              
  Lines         10998    11385     +387     
  Branches        784      837      +53     
============================================
+ Hits          10707    11094     +387     
  Misses          284      284              
  Partials          7        7              

Flag	Coverage Δ
sql-engine	97.44% <ø> (+0.08%)	⬆️

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

Impacted Files	Coverage Δ
...rch/sql/opensearch/setting/OpenSearchSettings.java	100.00% <ø> (ø)

... and 7 files with indirect coverage changes

[opensearch-trigger-bot]

The backport to 2.9 failed:

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

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-2.9 2.9
# Navigate to the new working tree
pushd ../.worktrees/backport-2.9
# Create a new branch
git switch --create backport/backport-1828-to-2.9
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 98ca9f861d81407b1df1840a64f6f4c6f8cd3775
# Push it to GitHub
git push --set-upstream origin backport/backport-1828-to-2.9
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/backport-2.9

Then, create a pull request where the base branch is 2.9 and the compare/head branch is backport/backport-1828-to-2.9.