Add ELSER inference API details

[lcawl]

Relates to #3821, elastic/elasticsearch#125187

This PR adds details and examples to the ELSER inference API, derived from https://www.elastic.co/guide/en/elasticsearch/reference/8.18/infer-service-elser.html

[github-actions]

Following you can find the validation results for the APIs you have changed.

API	Status	Request	Response
inference.put_elser	⚪	Missing test	Missing test

You can validate these APIs yourself by using the make validate target.

[github-actions]

Following you can find the validation results for the APIs you have changed.

API	Status	Request	Response
inference.put_elser	⚪	Missing test	Missing test

You can validate these APIs yourself by using the make validate target.

[github-actions]

Following you can find the validation results for the APIs you have changed.

API	Status	Request	Response
inference.put_elser	⚪	Missing test	Missing test

You can validate these APIs yourself by using the make validate target.

[github-actions]

The backport to 8.x 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-8.x 8.x
# Navigate to the new working tree
cd .worktrees/backport-8.x
# Create a new branch
git switch --create backport-4026-to-8.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 33420c6e0fddea1544cfaeca89ec6a178b3d0c1f
# Push it to GitHub
git push --set-upstream origin backport-4026-to-8.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-8.x

Then, create a pull request where the base branch is 8.x and the compare/head branch is backport-4026-to-8.x.

[github-actions]

The backport to 8.18 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-8.18 8.18
# Navigate to the new working tree
cd .worktrees/backport-8.18
# Create a new branch
git switch --create backport-4026-to-8.18
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 33420c6e0fddea1544cfaeca89ec6a178b3d0c1f
# Push it to GitHub
git push --set-upstream origin backport-4026-to-8.18
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-8.18

Then, create a pull request where the base branch is 8.18 and the compare/head branch is backport-4026-to-8.18.

[github-actions]

The backport to 9.0 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-9.0 9.0
# Navigate to the new working tree
cd .worktrees/backport-9.0
# Create a new branch
git switch --create backport-4026-to-9.0
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 33420c6e0fddea1544cfaeca89ec6a178b3d0c1f
# Push it to GitHub
git push --set-upstream origin backport-4026-to-9.0
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-9.0

Then, create a pull request where the base branch is 9.0 and the compare/head branch is backport-4026-to-9.0.

[lcawl]

💚 All backports created successfully

Status	Branch	Result
✅	9.0

Questions ?

Please refer to the Backport tool documentation

[lcawl]

💚 All backports created successfully

Status	Branch	Result
✅	8.x

Questions ?

Please refer to the Backport tool documentation

[lcawl]

💚 All backports created successfully

Status	Branch	Result
✅	8.18

Questions ?

Please refer to the Backport tool documentation