Migrate integration tests to built JS files

[JoshMock]

The integration test suite was previously generating and running unit tests in memory, which proves to be a complicated solution. This removes that test runner and replaces it with a test builder that generates JS files full of tap-compatible unit tests, and then runs them.

It also switches from using the yaml-rest-tests directory of the Elasticsearch repo to using the elasticsearch-clients-tests repo, which uses the same YAML format but the test suite is better optimized for testing client against language clients.

Many tests are skipped here, but notes are included as to why. This should run nearly 700 assertions successfully in approximately 3.5 minutes.

Hopefully will allow us to close #2315.

[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-2750-to-8.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 27774c9d3c5105a838673d6bded2c4af033f91d7
# Push it to GitHub
git push --set-upstream origin backport-2750-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-2750-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-2750-to-8.18
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 27774c9d3c5105a838673d6bded2c4af033f91d7
# Push it to GitHub
git push --set-upstream origin backport-2750-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-2750-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-2750-to-9.0
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 27774c9d3c5105a838673d6bded2c4af033f91d7
# Push it to GitHub
git push --set-upstream origin backport-2750-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-2750-to-9.0.