Setup: Allow for `wp-config-sample.php` to be formatted according to coding standards.

When the setup process reads `wp-config-sample.php`, it assumes that there are no spaces inside the brackes of the `define()`s. Unfortunately, this doesn't match our coding standards, so will no longer work correctly once we start enforcing them.

This also improves coding standards of the generated `wp-config.php` file.

See #41057.


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