cmd/cgo: improve cgoCheckPointer error message

When an unpinned Go pointer is passed to a C function, this error shows up:

> panic: runtime error: cgo argument has Go pointer to unpinned Go pointer
>
> goroutine 1 [running]:
> main.main.func1(...)
>         /mnt/go/src/test.go:15
> main.main()
>         /mnt/go/src/test.go:15 +0x79
> exit status 2

Retrieve the callee name, and use it in the error message.

> panic: runtime error: cgo argument of function main.main.func1 has Go pointer to unpinned Go pointer
>
> goroutine 1 [running]:
> main.main.func1(...)
>         /mnt/go/src/test.go:15
> main.main()
>         /mnt/go/src/test.go:15 +0x88
> exit status 2

Cc: Keith Randall <khr@golang.org>
Cc: Sean Liao <sean@liao.dev>
Cc: Ian Lance Taylor <iant@golang.org>
GH: #75856

Author: ariel-anieli

src/runtime/cgocall.go

@@ -535,10 +535,23 @@ var racecgosync uint64 // represents possible synchronization in C code
 // cgoCheckPointer checks if the argument contains a Go pointer that
 // points to an unpinned Go pointer, and panics if it does.
 func cgoCheckPointer(ptr any, arg any) {
+	var callerName string = " "
+
 	if !goexperiment.CgoCheck2 && debug.cgocheck == 0 {
 		return
 	}
 
+	pc, _, _, ok := Caller(1)
+	if ok {
+		function := FuncForPC(pc)
+
+		// Expected format of cgo callee name: A.B.C
+		if function != nil {
+			callerName += function.Name() + " "
+		}
+	}
+
+	cgoCheckPointerFail := "cgo argument of function" + callerName + "has Go pointer to unpinned Go pointer"
 	ep := efaceOf(&ptr)
 	t := ep._type
 
@@ -591,8 +604,6 @@ func cgoCheckPointer(ptr any, arg any) {
 	cgoCheckArg(t, ep.data, !t.IsDirectIface(), top, cgoCheckPointerFail)
 }
 
-const cgoCheckPointerFail = "cgo argument has Go pointer to unpinned Go pointer"
-
 // cgoCheckArg is the real work of cgoCheckPointer. The argument p
 // is either a pointer to the value (of type t), or the value itself,
 // depending on indir. The top parameter is whether we are at the top