Replace core:* to base:* where appropriate

core/testing/runner_windows.odin

@@ -3,8 +3,8 @@
 package testing
 
 import win32 "core:sys/windows"
-import "core:runtime"
-import "core:intrinsics"
+import "base:runtime"
+import "base:intrinsics"
 import "core:time"
 
 Sema :: struct {

core/testing/testing.odin

@@ -3,7 +3,7 @@ package testing
 import "core:fmt"
 import "core:io"
 import "core:time"
-import "core:intrinsics"
+import "base:intrinsics"
 import "core:reflect"
 
 _ :: reflect // alias reflect to nothing to force visibility for -vet