Return back-up slices for unavailable settings

When an inline slice is requested, and the setting is unavailable,
we should present more useful information to the user. This CL handles:
- Unsupported: return intent slice to Settings home page
- Disabled for user: intent to the setting page
- Unknown reason: intent to setting page
- Disabled dependency: Create intent-based Slice rather
than the requested inline slice.

Bug: 71640747
Test: robotests
Change-Id: I9c1a0ee36119d4f9f3b205e0824c251f4356db55

tests/robotests/src/com/android/settings/slices/FakeUnavailablePreferenceController.java

@@ -0,0 +1,21 @@
+package com.android.settings.slices;
+
+import android.content.Context;
+import android.provider.Settings;
+
+import com.android.settings.core.BasePreferenceController;
+
+public class FakeUnavailablePreferenceController extends BasePreferenceController {
+
+    public static final String AVAILABILITY_KEY = "fake_availability_key";
+
+    public FakeUnavailablePreferenceController(Context context) {
+        super(context, "key");
+    }
+
+    @Override
+    public int getAvailabilityStatus() {
+        return Settings.System.getInt(mContext.getContentResolver(),
+                AVAILABILITY_KEY, 0);
+    }
+}