Fix Netty4 header verifier inbound handler to deal with upgrade requests

[reta]

Description

Fix Netty4 header verifier inbound handler to deal with upgrade requests

Issues Resolved

Follow up on #5035

Testing

N/A

Check List

• New functionality includes testing
• New functionality has been documented
• New Roles/Permissions have a corresponding security dashboards plugin PR
• API changes companion pull request created
• Commits are signed per the DCO using --signoff

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.46%. Comparing base (d1894d4) to head (b98110a).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5045      +/-   ##
==========================================
- Coverage   71.50%   71.46%   -0.04%     
==========================================
  Files         336      336              
  Lines       22617    22617              
  Branches     3599     3599              
==========================================
- Hits        16172    16163       -9     
- Misses       4644     4652       +8     
- Partials     1801     1802       +1     

Files with missing lines	Coverage Δ
...sl/http/netty/Netty4HttpRequestHeaderVerifier.java	87.50% <ø> (ø)

... and 5 files with indirect coverage changes

[cwperks]

Should the changes in Netty4HttpRequestHeaderVerifier (i.e. DefaultHttpRequest -> HttpRequest) be backported to 2.x?

[reta]

Should the changes in Netty4HttpRequestHeaderVerifier (i.e. DefaultHttpRequest -> HttpRequest) be backported to 2.x?

I think it would be a good idea, for 3.x / 2.x mixed clusters that would be helpful, thanks @cwperks

[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/security/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/security/backport-2.x
# Create a new branch
git switch --create backport/backport-5045-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 2bef10c8754cd40754fc1dbc72a82b0dece25c9b
# Push it to GitHub
git push --set-upstream origin backport/backport-5045-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/security/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-5045-to-2.x.