Add the first flag to core_experiments_team_internal

Add an internal dir to host an aconfig file that is dedicated to
trunk_stable_workflow testing. We should use this one, instead the one
dedicated to the demo app.

Bug: 294537090
Change-Id: I1a28da8e202f5f454df35f298c8c962d3b9b229b

samples/AconfigDemo/internal/Android.bp

@@ -0,0 +1,9 @@
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+aconfig_declarations {
+    name: "trunk_stable_workflow_testing",
+    package: "com.android.trunk_stable_workflow_testing",
+    srcs: ["trunk_stable_workflow_test.aconfig"],
+}

samples/AconfigDemo/internal/trunk_stable_workflow_test.aconfig

@@ -0,0 +1,8 @@
+package: "com.android.trunk_stable_workflow_testing"
+
+flag {
+  name: "welcome_aboard"
+  namespace: "core_experiments_team_internal"
+  description: "Ahoy, raise the first flag of this namespace"
+  bug: "294537090"
+}