Implement permanent plugin architecture and update API

[tristanpoland]

This pull request makes significant improvements to the plugin API documentation and safety model, clarifies memory management practices, and simplifies several type definitions in the crates/plugin_editor_api/src/lib.rs file. The main focus is on ensuring ABI safety by never unloading plugin libraries, which enables safe sharing of function pointers, trait objects, and Arc<T> across the plugin boundary. It also updates the plugin interface to reflect these guarantees and removes outdated cleanup logic.

Plugin safety model and memory management [1] [2] [3]

• The documentation now clearly states that plugins are loaded once and never unloaded, ensuring function pointers, vtables, and drop glue remain valid for the process lifetime. This enables safe sharing of Arc<T>, trait objects, and function pointers, and removes the need for weak reference workarounds. Detailed guidance on preventing Arc cycles is added. [1] [2] [3]

API and trait changes [1] [2] [3]

• The EditorInstance trait is removed; plugins now return an Arc<dyn PanelView> directly, simplifying the interface and aligning with the new safety model. All documentation and examples are updated accordingly. [1] [2] [3]
• The plugin constructor function type (PluginCreate) is updated to return a 'static reference, and the destructor function is removed since plugins are never unloaded. The macro for exporting plugins is updated to reflect these changes.

Version compatibility and type simplification [1] [2] [3]

• Version checking is clarified: Rustc version must match exactly (ABI is not stable across versions), and only the semver part of the Rustc version is hashed for compatibility. [1] [2] [3]

Documentation improvements [1] [2] [3]

• Safety notes are added throughout the API, especially for function pointers and trait objects, explaining why they are safe to use. The statusbar button API is updated with clearer safety documentation. [1] [2] [3]

Minor code and formatting cleanups [1] [2] [3] [4] [5]

• Several enums and structs are reformatted for conciseness, and redundant code (such as the EditorLogger and its usages) is removed. Minor formatting and documentation corrections are made throughout. [1] [2] [3] [4] [5]