refactor: migrate `@include` to `@apply`

What does this MR do?

Migrate @include to @apply

This migrates @include directives to @apply using the updated migration script. This leaves us with some occurrences that the script ignored because the Tailwind equivalent has the same name. In those cases, we should be able to manually search and replace.

Migration command:

./bin/migrate_custom_utils_to_tw.mjs -d ./src

note: This command also changed some files in src/scss/utility-mixins. I've reverted those as there's no point in migrating the legacy mixins which we'll remove in the near future.