Add static setting for checkPendingFlushUpdate functionality of lucene index writer (#6728)

* Added static setting for checkPendingFlushUpdate functionality of lucene writer

Signed-off-by: Prabhat Sharma <ptsharma@amazon.com>

* Update _install-and-configure/configuring-opensearch/index-settings.md

Co-authored-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>
Signed-off-by: Prabhat <20185657+CaptainDredge@users.noreply.github.com>

* Added static setting for checkPendingFlushUpdate functionality of lucene writer

Signed-off-by: Prabhat Sharma <ptsharma@amazon.com>

* Update _install-and-configure/configuring-opensearch/index-settings.md

Co-authored-by: Nathan Bower <nbower@amazon.com>
Signed-off-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>

---------

Signed-off-by: Prabhat Sharma <ptsharma@amazon.com>
Signed-off-by: Prabhat <20185657+CaptainDredge@users.noreply.github.com>
Signed-off-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>
Co-authored-by: Prabhat Sharma <ptsharma@amazon.com>
Co-authored-by: kolchfa-aws <105444904+kolchfa-aws@users.noreply.github.com>
Co-authored-by: Nathan Bower <nbower@amazon.com>

Author: 4 people

_install-and-configure/configuring-opensearch/index-settings.md

@@ -100,6 +100,7 @@ OpenSearch supports the following static index-level index settings:
 
 - `index.merge_on_flush.policy` (default | merge-on-flush): This setting controls which merge policy should be used when `index.merge_on_flush.enabled` is enabled. Default is `default`.
 
+- `index.check_pending_flush.enabled` (Boolean): This setting controls the Apache Lucene `checkPendingFlushOnUpdate` index writer setting, which specifies whether an indexing thread should check for pending flushes on an update in order to flush indexing buffers to disk. Default is `true`.
 
 ### Updating a static index setting