[fuchsia][v8_unittests] move to Fuchsia SDK package templates

Use the `fuchsia_component` and `fuchsia_package` GN templates from the
Fuchsia SDK to package the `v8_unittests` test for Fuchsia. Give the
`v8_unittests` their own dedicated `.cmx` file, instead of depending on
`v8.cmx`.

Bug: chromium:1256503
Change-Id: I22788359bed18eb643e288ee1a0c92c24c0dc3e1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3819644Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Commit-Queue: Derek Gonyeo <dgonyeo@google.com>
Cr-Commit-Position: refs/heads/main@{#82656}

test/unittests/BUILD.gn

@@ -7,11 +7,16 @@ import("../../gni/v8.gni")
 if (is_fuchsia) {
   import("//build/config/fuchsia/rules.gni")
 
-  cr_fuchsia_package("v8_unittests_pkg") {
+  fuchsia_component("v8_unittests_component") {
     testonly = true
-    binary = ":unittests"
-    manifest = "../../gni/v8.cmx"
-    package_name_override = "v8_unittests"
+    data_deps = [ ":unittests" ]
+    manifest = "v8_unittests.cmx"
+  }
+
+  fuchsia_package("v8_unittests_pkg") {
+    testonly = true
+    package_name = "v8_unittests"
+    deps = [ ":v8_unittests_component" ]
   }
 
   fuchsia_test_runner("v8_unittests_fuchsia") {

test/unittests/v8_unittests.cmx

+{
+  "program": {
+    "binary": "unittests"
+  },
+  "facets": {
+    "fuchsia.test": {
+      "system-services": [
+      "fuchsia.kernel.VmexResource"
+      ]
+    }
+  },
+  "sandbox": {
+    "features": [
+      "deprecated-ambient-replace-as-executable",
+      "isolated-persistent-storage",
+      "isolated-temp"
+    ],
+    "services": [
+      "fuchsia.kernel.VmexResource",
+      "fuchsia.logger.LogSink",
+      "fuchsia.process.Launcher"
+    ]
+  }
+}