fix concurrent modification exceptions in thread context

[ansjcy]

Description

Current implementation to inject headers in thread context caused concurrent modification errors since other threads can access the headers at the same time when we delete it.

java.lang.AssertionError: Unexpected ShardFailures: [shard [[6aZksFMiT4WtFkh9Ni-mog][test][7]], reason [RemoteTransportException[[node_t2][127.0.0.1:35247][indices:data/read/search[phase/query/id]]]; nested: NotSerializableExceptionWrapper[concurrent_modification_exception: null]; ], cause [NotSerializableExceptionWrapper[concurrent_modification_exception: null]
	at java.util.HashMap$HashIterator.nextNode(HashMap.java:1605)
	at java.util.HashMap$EntryIterator.next(HashMap.java:1638)
	at java.util.HashMap$EntryIterator.next(HashMap.java:1636)
	at org.opensearch.common.util.concurrent.ThreadContext$ThreadContextStruct.putResponseHeaders(ThreadContext.java:710)
	at org.opensearch.common.util.concurrent.ThreadContext.lambda$newStoredContext$4(ThreadContext.java:278)
	at org.opensearch.common.util.concurrent.ThreadContext$StoredContext.restore(ThreadContext.java:568)
	at org.opensearch.transport.RequestHandlerRegistry.processMessageReceived(RequestHandlerRegistry.java:112)
	at org.opensearch.transport.NativeMessageHandler.handleRequest(NativeMessageHandler.java:279)
	at org.opensearch.transport.NativeMessageHandler.handleMessage(NativeMessageHandler.java:147)
	at org.opensearch.transport.NativeMessageHandler.messageReceived(NativeMessageHandler.java:127)
	at org.opensearch.transport.InboundHandler.messageReceivedFromPipeline(InboundHandler.java:121)
	at org.opensearch.transport.InboundHandler.inboundMessage(InboundHandler.java:113)
	at org.opensearch.transport.TcpTransport.inboundMessage(TcpTransport.java:788)
	at org.opensearch.transport.nativeprotocol.NativeInboundBytesHandler.forwardFragments(NativeInboundBytesHandler.java:156)
	at org.opensearch.transport.nativeprotocol.NativeInboundBytesHandler.doHandleBytes(NativeInboundBytesHandler.java:93)
	at org.opensearch.transport.InboundPipeline.doHandleBytes(InboundPipeline.java:143)
	at org.opensearch.transport.InboundPipeline.handleBytes(InboundPipeline.java:119)
	at org.opensearch.transport.nio.MockNioTransport$MockTcpReadWriteHandler.consumeReads(MockNioTransport.java:343)
	at org.opensearch.nio.SocketChannelContext.handleReadBytes(SocketChannelContext.java:246)
	at org.opensearch.nio.BytesChannelContext.read(BytesChannelContext.java:59)
	at org.opensearch.nio.EventHandler.handleRead(EventHandler.java:152)
	at org.opensearch.transport.nio.TestEventHandler.handleRead(TestEventHandler.java:167)
	at org.opensearch.nio.NioSelector.handleRead(NioSelector.java:438)
	at org.opensearch.nio.NioSelector.processKey(NioSelector.java:264)
	at org.opensearch.nio.NioSelector.singleLoop(NioSelector.java:191)
	at org.opensearch.nio.NioSelector.runLoop(NioSelector.java:148)
	at java.lang.Thread.run(Thread.java:1583)
]]
Expected: <0>
     but: was <1>

This is caused by removing a key from a map while other threads are iterating the map at the same time.
This PR removes the delete logic and make replacing existing key logic self contained in put headers function.

Related Issues

Related to the above build failure

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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.

[deshsidd]

LGTM apart from the minor comment. Will approve after the change

[github-actions]

❕ Gradle check result for 666af8c: UNSTABLE

Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.69%. Comparing base (b15cb0c) to head (95bcf01).
Report is 371 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #14084      +/-   ##
============================================
+ Coverage     71.42%   71.69%   +0.27%     
- Complexity    59978    61622    +1644     
============================================
  Files          4985     5082      +97     
  Lines        282275   289233    +6958     
  Branches      40946    41853     +907     
============================================
+ Hits         201603   207360    +5757     
- Misses        63999    64732     +733     
- Partials      16673    17141     +468     

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[github-actions]

❌ Gradle check result for 86c4909:

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions]

❌ Gradle check result for 768da23:

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions]

❌ Gradle check result for 70f95c0: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions]

✅ Gradle check result for 95bcf01: SUCCESS

[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/OpenSearch/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/OpenSearch/backport-2.x
# Create a new branch
git switch --create backport/backport-14084-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 c8f0b6da6def4b8e78cd17274e5a4271e844a71f
# Push it to GitHub
git push --set-upstream origin backport/backport-14084-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/OpenSearch/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-14084-to-2.x.