deprecating local param from alias req

[l-trotta]

Following #3059, which removes the local parameter from alias requests in version 9, we should mark it as deprecated in 8

[github-actions]

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

API	Status	Request	Response
indices.exists_alias	🟢	38/38	38/38
indices.get_alias	🔴	82/82	73/82

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

[github-actions]

The backport to 8.15 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-8.15 8.15
# Navigate to the new working tree
cd .worktrees/backport-8.15
# Create a new branch
git switch --create backport-3094-to-8.15
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 7c12ea069c93716a6ac243d6979c977a1669d914
# Push it to GitHub
git push --set-upstream origin backport-3094-to-8.15
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-8.15

Then, create a pull request where the base branch is 8.15 and the compare/head branch is backport-3094-to-8.15.