Introduce Plugin Groups For Loading Organization

[hGriff0n]

Integrates the concept of plugin "groups" from the old Plugin Groups, rebasing the prior loading options into auto-generated groups. Reimplements the existing loading mechanism to use plugin groups for the purpose of enabling future extensibility via custom groups.

This does not include the addition of any settings/ui elements for creating and editing groups as creating a "usable UI" is not really my forte (let alone, one matching the existing design language). I'm also new to Obsidian plugin development and so these changes are not explicitly tested as my system is not setup for it at the moment (can do, just don't know yet if this is a one off).

Summary:

• Introduce new settings object PluginGroupSettings which defines a customization point for plugin loading options
  • Groups can customize whether they are enabled by default on startup as well as the delay before loading
  • Also provides options supporting future directions, such as "generating enable/disable commands"
• Implements the existing loading methods ("Disabled", "Instant", "Short Delay", "Long Delay") as default plugin groups
• Maintains backwards compatibility by assigning plugins to groups based on their saved "loading method" setting (if not indicated from the save data)