[fuchsia] Rename fuchsia_package() rule to cr_fuchsia_package().

Fuchsia's SDK will soon provide GN rules include one for declaring
fuchsia package targets. Since the SDK-provided rule works differently
from the Chromium one but is called fuchsia_package(), we need to rename
the Chromium rule to avoid them clashing.

Bug: chromium:1050703
Change-Id: Ia2fcba8e32f311e6859590d9c95730ffe6875192
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2050388Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66244}

test/unittests/BUILD.gn

@@ -7,7 +7,7 @@ import("../../gni/v8.gni")
 if (is_fuchsia) {
   import("//build/config/fuchsia/rules.gni")
 
-  fuchsia_package("v8_unittests_pkg") {
+  cr_fuchsia_package("v8_unittests_pkg") {
     testonly = true
     binary = ":unittests"
     package_name_override = "v8_unittests"