compiler: disallow most types in //go:wasmimport

This is for compatibility with upstream Go.
See https://github.com/golang/go/issues/59149 for more context.

compiler/testdata/errors.go

@@ -1 +1,43 @@
 package main
+
+import "unsafe"
+
+//go:wasmimport modulename empty
+func empty()
+
+// ERROR: can only use //go:wasmimport on declarations
+//
+//go:wasmimport modulename implementation
+func implementation() {
+}
+
+type Uint uint32
+
+//go:wasmimport modulename validparam
+func validparam(a int32, b uint64, c float64, d unsafe.Pointer, e Uint)
+
+// ERROR: //go:wasmimport modulename invalidparam: unsupported parameter type int
+// ERROR: //go:wasmimport modulename invalidparam: unsupported parameter type string
+// ERROR: //go:wasmimport modulename invalidparam: unsupported parameter type []byte
+// ERROR: //go:wasmimport modulename invalidparam: unsupported parameter type *int32
+//
+//go:wasmimport modulename invalidparam
+func invalidparam(a int, b string, c []byte, d *int32)
+
+//go:wasmimport modulename validreturn
+func validreturn() int32
+
+// ERROR: //go:wasmimport modulename manyreturns: too many return values
+//
+//go:wasmimport modulename manyreturns
+func manyreturns() (int32, int32)
+
+// ERROR: //go:wasmimport modulename invalidreturn: unsupported result type int
+//
+//go:wasmimport modulename invalidreturn
+func invalidreturn() int
+
+// ERROR: //go:wasmimport modulename invalidUnsafePointerReturn: unsupported result type unsafe.Pointer
+//
+//go:wasmimport modulename invalidUnsafePointerReturn
+func invalidUnsafePointerReturn() unsafe.Pointer