Bug 1894239: Enable MOZ_SELECTABLE_PROFILES by default. r=jhirsch,omc-reviewers,niklas,emcminn,mconley

This also removes some tests of `MOZ_SELECTABLE_PROFILES` from `browser/components/profiles` files
where the test is pointless because that test is excluded from the build if `MOZ_SELECTABLE_PROFILES`
is unset.

Differential Revision: https://phabricator.services.mozilla.com/D227372

browser/components/asrouter/modules/ASRouterTargeting.sys.mjs

@@ -588,9 +588,9 @@ const TargetingGetters = {
   },
   get canCreateSelectableProfiles() {
     if (!AppConstants.MOZ_SELECTABLE_PROFILES) {
-      return null;
+      return false;
     }
-    return !!lazy.SelectableProfileService?.groupToolkitProfile;
+    return lazy.SelectableProfileService?.isEnabled ?? false;
   },
   get hasSelectableProfiles() {
     return !!lazy.profileStoreID;