fix(interp): convert bin interface to src interface.

[laushunyu]

fix: #1558

test case:

package main

import "fmt"

type A struct {
}

func (a A) String() string {
	return "String"
}

func (a A) GoString() string {
	return "GoString"
}

type Stringer interface {
	String() string
}

type GoStringer interface {
	GoString() string
}

func Fuck(in fmt.Stringer) {
	var a Stringer = A{}

	{
		t, ok := a.(GoStringer)
		fmt.Printf("src to src: %v\n", ok)
		if ok {
			fmt.Println(t.GoString())
		}
	}

	{
		t, ok := a.(fmt.GoStringer)
		fmt.Printf("src to src: %v\n", ok)
		if ok {
			fmt.Println(t.GoString())
		}
	}

	{
		t, ok := in.(GoStringer)
		fmt.Printf("bin to src: %v\n", ok)
		if ok {
			fmt.Println(t.GoString())
		}
	}

	{
		t, ok := in.(fmt.GoStringer)
		fmt.Printf("bin to bin: %v\n", ok)
		if ok {
			fmt.Println(t.GoString())
		}
	}
}

runner:

package main

import (
	"fmt"
	"github.com/traefik/yaegi/interp"
	"github.com/traefik/yaegi/stdlib"
	"os"
)

type B struct {
}

func (a B) String() string {
	return "String"
}

func (a B) GoString() string {
	return "GoString"
}

func main() {
	interpreter := interp.New(interp.Options{
		SourcecodeFilesystem: os.DirFS("_lib"),
	})
	interpreter.Use(stdlib.Symbols)

	_, err := interpreter.CompilePath("fuck")
	if err != nil {
		panic(err)
	}

	mainSymbols := interpreter.Symbols("fuck")["fuck"]
	fn := mainSymbols["Fuck"].Interface().(func(stringer fmt.Stringer))
	fn(B{})
}

output:

src to src: true
GoString
src to src: true
GoString
bin to src: true
GoString
bin to bin: true
GoString

it works, but i dont know whether the fix will cause more bugs....