print minified css for global styles

[aristath]

Description

For development purposes adding tabs and linebreaks to the generated styles makes sense since it makes things easier to read. But for production and code that is going to be shipped to millions of websites, we should try to minimize our footprint as much as possible.
This PR modifies the generated CSS from global styles so they don't include tabs, spaces, and linebreaks.
Every byte counts.

How has this been tested?

Tested that the same styles get generated and printed, the only thing that changes is whitespace.

Types of changes

Removed whitespace characters from the gutenberg_experimental_global_styles_resolver_styles function.

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR.

[oandregal]

What do you think of using SCRIPT_DEBUG to decide which version (dev or prod) to output?

[aristath]

What do you think of using SCRIPT_DEBUG to decide which version (dev or prod) to output?

Good idea, added an extra check for that.
The CSS will now be printed with whitespace when using SCRIPT_DEBUG, and minified when on production 👍

[oandregal]

This works nicely, thanks!