ES|QL query builder robustness fixes

[miguelgrinberg]

Several fixes intended to make the new ES|QL query builder more robust:

• Add a documentation section on using parameters to prevent code injection attacks
• Expose the E() function through the elasticsearch.esql module
• Better formatting and escaping of identifiers, index names and ES|QL expressions in rendered queries
• Updated syntax of the COMPLETION command
• Moved ES|QL integration tests under test_integration as should be expected
• Added some more tests with the use of parameters

[github-actions]

🔍 Preview links for changed docs

• docs/reference/esql-query-builder.md

[github-actions]

The backport to 8.19 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-8.19 8.19
# Navigate to the new working tree
cd .worktrees/backport-8.19
# Create a new branch
git switch --create backport-3017-to-8.19
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 e3e85ed38c303b792cd44f892c961c3c45804c55
# Push it to GitHub
git push --set-upstream origin backport-3017-to-8.19
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-8.19

Then, create a pull request where the base branch is 8.19 and the compare/head branch is backport-3017-to-8.19.