Update engine for version 2.19 or above

[VijayanB]

Description

We changed default engine from NMSLIB to FAISS on 2.18. Hence, for use case where mode is not configured and compression is 1x or undefined we default to nmslib since cosine similarity was not supported. From 2.19, we added support to cosine, so, we can now change it to faiss for no compression or 1x compression to align with our strategy on deprecating nmslib in future releases.

Related Issues

Resolves #[Issue number to be closed when this PR is merged]

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.

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[VijayanB]

Added this PR directly to release note and added skip change log

[VijayanB]

@naveentatikonda looks like integration test is crashing cluster. is this related to gcc issue? This is only happening for linux CI

[naveentatikonda]

@naveentatikonda looks like integration test is crashing cluster. is this related to gcc issue? This is only happening for linux CI

Yes, looks like that. Peter is working on making the changes to image which will build nmslib using gcc-10

[opensearch-trigger-bot]

The backport to main failed:

The process '/usr/bin/git' failed with exit code 1

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-main main
# Navigate to the new working tree
cd .worktrees/backport-main
# Create a new branch
git switch --create backport/backport-2501-to-main
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 8ee82b9528de4767ffa7bf96f1e51d5895761db7
# Push it to GitHub
git push --set-upstream origin backport/backport-2501-to-main
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-main

Then, create a pull request where the base branch is main and the compare/head branch is backport/backport-2501-to-main.