Build/Test Tools: Comment on PRs with WordPress Playground information.

After [56958], pull requests to `wordpress-develop` can be tested within a WordPress Playground instance. However this capability is not obvious.

This makes several updates to GitHub action workflows to avoid unnecessary extra runs/jobs while also commenting on pull requests with proper context for testing in Playground once a build is available for the PR.

Changes:
- The `build.yml` workflow has been deleted. The WordPress build process is already being tested within the `test-build-processes.yml` workflow. Now that workflow will produce and upload the built artifact for the given PR.
- A `pull-request-comments.yml` workflow has been added to handle the commenting. To avoid having multiple workflows that comment on PRs, the logic within the `welcome-new-contributors.yml` workflow has been merged into this one.
- The `pull_request` event trigger lacks the needed permission to comment on or update pull requests. Instead of using `pull_request_target` to navigate around this, the `test-build-processes.yml` workflow will now use `workflow_dispatch` to initiate a run of the commenting workflow. This adds the ability to only comment on the PR when a build has been successfully created and uploaded as an artifact.

Props swissspidy, zieladam, jeffpaul.
See #59416.
Built from https://develop.svn.wordpress.org/trunk@57124


git-svn-id: http://core.svn.wordpress.org/trunk@56635 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.5-alpha-57123';
+$wp_version = '6.5-alpha-57124';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.