[build] Use run_test_component from testing

The //garnet/packages/tests:run_test_component target also includes
tests for run_test_component. We shouldn't require that those tests be
built and run whenever run_test_component is used, so I'm splitting the
tests into their own group separate from run_test_component itself.

Bug: 44580
Change-Id: I2a4d84d0eba64e1c2a5d2996800a2497f6183832
diff --git a/BUILD.gn b/BUILD.gn
index 82224c7..55f2701 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -77,7 +77,7 @@
                   # TODO: This target should just aggregate the top-level directories and
                   # most of these dependencies should be in those subdirectories.
                   "//garnet/packages:garnet",
-                  "//garnet/packages/tests:run_test_component",
+                  "//garnet/packages/testing:run_test_component",
                   "//garnet/packages/tests:scenic",
                   "//garnet/packages/tools:scenic",
                   "//src/modular/bundles:framework_experimental",