Leverage PluginSettingsInterface::settingsSummary() in LayersPanel

Problem/Motivation

Scaffold panel has ::buildComponentSettingItem() private static method which is hardcoding logic from SDC and the Icon API, and mixing it with the building of renderable arrays. Done

Proposed resolution

In order to keep only the renderable logic in LayersPanel::addComponentSettingsSummary() and be future-proof, can we move the data logic to implementations of PluginSettingsInterface::settingsSummary()?

• ComponentSource::settingsSummary() #3616786: Proper settingsSummary
• IconRenderableSource::settingsSummary()
• IconSource::settingsSummary()

Remaining tasks

For UI Icons see : 3591885

By removing hardcoded SDC logic, this will also help the work on #3531521: Layout plugins support. Done