[test][utf_conversion] Relocate unit tests to exist alongside source

Change-Id: I8cd0ba4f4ae1af47271462a6da8ddcd7813a19d8

zircon/system/utest/utf_conversion/BUILD.gn → zircon/system/ulib/utf_conversion/test/BUILD.gn

@@ -2,6 +2,13 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+group("test") {
+  testonly = true
+  deps = [
+    ":utf_conversion",
+  ]
+}
+
 test("utf_conversion") {
   sources = [
     "main.cpp",

zircon/system/utest/BUILD.gn

@@ -94,6 +94,7 @@ if (current_cpu != "") {
       "$zx/system/ulib/tftp:tftp-test",
       "$zx/system/ulib/trace-reader:tests",
       "$zx/system/ulib/trace-vthread:tests",
+      "$zx/system/ulib/utf_conversion/test",
       "$zx/system/ulib/zbi-bootfs/test",
       "$zx/system/ulib/zx/test",
       "$zx/system/ulib/zxio/test",
@@ -184,7 +185,6 @@ if (current_cpu != "") {
       "trace",
       "usb",
       "usb-virtual-bus",
-      "utf_conversion",
       "util",
       "vdso",
       "vdso-base",