perf!: cache UserData fields

[sxyazi]

This PR fixes a longstanding issue in the plugin system where every field access triggers redundant memory allocation. For example, when getting the currently selected file Url:

cx.active.current.hovered.url
cx.active.current.cwd
-- ...

Every time the .url field is accessed, a new Url is allocated. During UI rendering, these Urls are used repeatedly in multiple render functions, leading to unnecessary memory allocation.

Also, each access of .active, .current, and .hovered creates a new UserData. Although UserData is lighter compared to Urls, they still all need to be destroyed after rendering ends.

With this PR, these field accesses will be globally cached and created only once. This means that every function will share the same object, avoiding repeated memory allocation and destruction.

⚠️ Breaking changes

• The methods frag, name, stem, ext, and parent on Url are now properties.
• The method name on tab::Tab is now a property.
• The method is_hovered on fs::File is now a property.

For instance:

- local name = url:name()
+ local name = url.name

Previously, these were methods to hint that each call would create a new object. With field caching, they are now treated as cacheable properties and are guaranteed to allocate memory at most once on access, simplifying the code at the same time.

[boydaihungst]

ya.manager_emit/ya.mgr_emit throw this error, also new:

  2025-04-04T20:27:57.202500Z ERROR yazi::app::commands::plugin: Sync plugin `json` failed: unsupported userdata included
stack traceback:
	[C]: in field 'mgr_emit'
	[string "code"]:21: in function 'code.seek'
	>[C]: in method 'seek'
	?: in function 'json.seek'

    at yazi-fm/src/app/commands/plugin.rs:79

Also extract.lua plugin still using old :parent() instead of .parent: https://github.com/sxyazi/yazi/blob/75fad253c0948a06bcfed57b99ca60ecca39a0c3/yazi-plugin/preset/plugins/extract.lua#L42C13-L42C26

[sxyazi]

Thanks for reporting, fixed in 9565c1b

[boydaihungst]

@sxyazi This also broke plugin vcs-files:
https://github.com/yazi-rs/plugins/blob/9a095057d698aaaedc4dd23d638285bd3fd647e9/vcs-files.yazi/main.lua#L26

Here is the error message.

Failed to run the plugin:
userdata is not expected type
stack traceback:
	[C]: in field 'op'
	[string "vcs-files"]:29: in function <[string "vcs-files"]:7>

[sxyazi]

Fixed in fd007ab