feat!: custom preloader & previewer

[sxyazi]

This marks a milestone in the "Yazi concurrent plugin system". I spent a lot of time thinking how to build it - prioritizing efficiency while ensuring scalability. To achieve this:

• All I/O tasks are asynchronous and concurrent, even including the plugins themselves.
• Previewers/preloaders for all file formats are re-implemented as Lua plugins (CPU-bound tasks are still in Rust).
• The entire file system has been rewritten - no more frequent directory list reads to keep things up-to-date. Instead, heuristic updates for changed files are in place.
• UI rendering is done in a separate thread through Lua plugins, enabling concurrent rendering. This is useful for CPU-bound tasks like code highlighting, JSON preview, external escape sequences, and custom components. The entire process is discardable (IO/CPU).
• More granular control over task cancellation: leveraging Lua, task discarding isn't restricted to just I/O. CPU tasks can now also be discarded - checking for discarding during function calls, returns, and fixed instructions have executed.
• New mixed media preview mode: imagine displaying file metadata (e.g., video duration, resolution, color space) above or below the preview image simultaneously.

I think I made it; Yazi will be faster than ever before! Note: This is a breaking change set to be released as Yazi v0.2.0. If you have time, please help us in testing it! 🙏🏻

If you're interested in creating your own preloader or previewer, there are some built-in examples here: https://github.com/sxyazi/yazi/tree/main/yazi-plugin/preset/plugins. I'll release the new plugin API documentation at https://yazi-rs.github.io soon.

• Closes [Feature Request] Custom Preview Commands #182 - @Neurognostic
• Fixes image previews not updated #261 - @joalof
• Fixes PDF seek #425 - @MinaMatta98
• This PR includes much of the implementation for the plugin system, but I still need some design thinking and will finalize it in subsequent PRs.

Breaking changes:

See Migrating to Yazi v0.2.0.

Tagging the owners of affected repos as a headsup:

https://github.com/search?q=ui.Base%28+yazi+NOT+is%3Afork&type=code

• https://github.com/angelocordero/nixos-config @angelocordero
• https://github.com/Matt-FTW/dotfiles @Matt-FTW
• https://github.com/huwqchn/.dotfiles @huwqchn