wit, wit/bindgen: generate Go type aliases for WIT type aliases

[ydnar]

Go type aliases are now generated for each WIT type alias (type foo = bar). Deep chains of type aliases (type b = a; type c = b;) are fully supported. Generated documentation now reflects whether a type is an alias.

For example, given the following WIT:

package example:aliases;

interface i {
	resource r {
		m: func() -> u32;
	}

	type a = r;
	type b = a;
	type c = b;

	fa: func(v: a);
	fb: func(v: b);
	fc: func(v: c);
}

world w {
	import i;
	export i;
}

Generates the following Go:

// R represents the imported resource "example:aliases/i#r".
//
//	resource r
type R cm.Resource

// A represents the imported type alias "example:aliases/i#a".
//
// See [R] for more information.
type A = R

// B represents the imported type alias "example:aliases/i#b".
//
// See [A] for more information.
type B = A

// C represents the imported type alias "example:aliases/i#c".
//
// See [B] for more information.
type C = B

Fixes #204.

[deadprogram]

Just verified that this PR does what it says it does. Thank you very much for such a quick response @ydnar