Define SCRIPT_DEBUG early, similarly to WP_DEBUG

[azaozz]

Currently SCRIPT_DEBUG in defined in script-loader.php. That is about half-way through loading of WordPress.

This will not impact any plugins as script-loader.php is already included by the time plugins are loaded. It will make SCRIPT_DEBUG always available and prevent errors similar to #32118.

[azaozz]

We will still need the check at the top of script-loader.php as that file is included directly when concatenating scripts and stylesheets.

[azaozz]

In 32935:

Define SCRIPT_DEBUG early on every load, similarly to WP_DEBUG. Remove defined( 'SCRIPT_DEBUG' ) checks.
Fixes #32333.