Build Tools: Miscellaneous `local-env` improvements.

- Move the functionality for controlling `local-env` out of `package.json`, into JS scripts.
- Merge the `docker-compose` config files, and move it to the root directory. This allows `docker-compose.override.yml` to work for local overrides.
- Fix nginx redirecting to port 80 under some circumstances.
- `npm run env:install` now creates `wp-tests.config.php` for you.
- Cleaned up a bunch of cruft in `.travis.yml`.

See #47767.


Built from https://develop.svn.wordpress.org/trunk@45783


git-svn-id: http://core.svn.wordpress.org/trunk@45594 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.3-alpha-45782';
+$wp_version = '5.3-alpha-45783';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.