Output x-state instead of x-technical-preview and x-available-since

[lcawl]

Relates to #2714, #2609

Rather than implementing x-technical-preview and x-available-since, Bump.sh is going to use x-state. This PR updates the openAPI generator to reflect that change.

[l-trotta]

LGTM!

[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-2989-to-8.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 dbde402095f807085e15699f7c0ae608ff96a887
# Push it to GitHub
git push --set-upstream origin backport-2989-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-2989-to-8.x.