rs port: update all docs for using the new `Handle` API.

[fahdfady]

📚 Documentation

we exposed a new API Handle via this issue #589
now, the function signatures and usages are changed. we need to update the documentation, this for example:

core/source/ports/rs_port/src/load.rs

Lines 99 to 108 in bc073fc

	/// Loads a file from a single file. Usage example: ...
	/// ```
	/// // A Nodejs path
	/// metacall::load::from_single_file("node", "index.js").unwrap();
	/// ```
	pub fn from_single_file(
	tag: Tag,
	path: impl AsRef<Path>,
	handle: Option<&mut Handle>,
	) -> Result<(), MetaCallLoaderError> {