checker: fix generic method calls with multi generic types (fix #20330)

[shove70]

1. Fixed Generic method for a generic struct expects the struct's type #20330
2. Add tests.

module main

struct Test[T] {}

fn (t Test[T]) abc[U]() {
	t.xyz[U]()
}

fn (t Test[T]) xyz[U]() {}

fn main() {
	t := Test[string]{}
	t.abc[f32]()
	t.abc[u32]()
}

outputs:

passed

[shove70]

CI seems unrelated.

[spytheman]

CI seems unrelated.

Yes, vinix changed :-| . I've disabled the CI workflow for now, and will fix it soon.

[spytheman]

Excellent work.