checker: strengthen the judgment of generic type parameters replacement

[yuyi98]

This PR strengthen the judgment of generic type parameters replacement and merge two tests into one.

struct Response<U> {
	result U
}

fn send_1<A, B>(res A, b B) string {
	msg := Response<U>{
		result: res
	}
	println(b)
	return '$msg'
}

fn send_2<A, B>(res A, b B) string {
	msg := Response<A, B>{
		result: res
	}
	println(b)
	return '$msg'
}

fn main() {
	mut ret := send_1(123, 22.2)
	println(ret)

	ret = send_2(123, 22.2)
	println(ret)
}

PS D:\Test\v\tt1> v run .
./tt1.v:6:9: error: generic struct init type parameter `U` must be within the parameters `(A,B)` of the current generic function
    4 |
    5 | fn send_1<A, B>(res A, b B) string {
    6 |     msg := Response<U>{
      |            ~~~~~~~~~~~~
    7 |         result: res
    8 |     }
./tt1.v:7:3: error: cannot assign to field `result`: expected `U`, not `int`
    5 | fn send_1<A, B>(res A, b B) string {
    6 |     msg := Response<U>{
    7 |         result: res
      |         ~~~~~~~~~~~
    8 |     }
    9 |     println(b)
./tt1.v:14:9: error: generic struct init expects 1 generic parameter, but got 2
   12 |
   13 | fn send_2<A, B>(res A, b B) string {
   14 |     msg := Response<A, B>{
      |            ~~~~~~~~~~~~~~~
   15 |         result: res
   16 |     }
./tt1.v:15:3: error: cannot assign to field `result`: expected `U`, not `int`
   13 | fn send_2<A, B>(res A, b B) string {
   14 |     msg := Response<A, B>{
   15 |         result: res
      |         ~~~~~~~~~~~
   16 |     }
   17 |     println(b)