Move Iconify Icons global settings into CKEditor plugin settings

Problem/Motivation

The Iconify Icons CKEditor5 plugin currently retrieves icon collections from a global configuration. This presents a limitation: the same collections are applied uniformly across all rich text formats, restricting customization and flexibility.

Proposed resolution

To enhance user control, the global settings for selecting available icon collections should be moved to the CKEditor5 plugin settings. This adjustment would allow users to choose different icon collections for each specific rich text format, offering greater customization and adaptability.