WordPress Core is not really custom and does not reference "custom post type" in its function naming. This commit renames 2 public static methods:
* `WP_Theme_JSON_Resolver::get_user_custom_post_type_id()` renamed to `WP_Theme_JSON_Resolver::get_user_global_styles_post_id()`.
* `WP_Theme_JSON_Resolver::get_user_data_from_custom_post_type()` renamed to `WP_Theme_JSON_Resolver:: get_user_data_from_wp_global_styles()`.
Follow-up to [52049], [52051], [52069], [52232], [52275], [52364].
Props antonvlasenko, bernhard-reiter, costdev, desrosj, hellofromTonya, noisysocks, oandregal, SergeyBiryukov.
Fixes#54517.
Built from https://develop.svn.wordpress.org/trunk@52372
git-svn-id: http://core.svn.wordpress.org/trunk@51964 1a063a9b-81f0-0310-95a4-ce76da25c4cd