luci-app-mosdns: use the fallback plugin to process apple domain names

* Using `always_standby` can improve query efficiency

luci-app-mosdns/root/usr/share/mosdns/default.yaml

@@ -114,6 +114,13 @@ plugins:
       upstreams:
         - addr: remote_dns
 
+  - tag: forward_remote_upstream
+    type: sequence
+    args:
+      - exec: prefer_ipv4
+      - exec: ecs_remote
+      - exec: $forward_remote
+
   - tag: modify_ttl
     type: sequence
     args:
@@ -124,18 +131,6 @@ plugins:
     args:
       - exec: ttl 5-5
 
-  - tag: local_sequence
-    type: sequence
-    args:
-      - exec: $forward_local
-
-  - tag: remote_sequence
-    type: sequence
-    args:
-      - exec: prefer_ipv4
-      - exec: ecs_remote
-      - exec: $forward_remote
-
   - tag: has_resp_sequence
     type: sequence
     args:
@@ -148,66 +143,65 @@ plugins:
       - matches: has_resp
         exec: accept
 
-  - tag: query_is_local_ip
+  - tag: query_is_non_local_ip
     type: sequence
     args:
-      - exec: $local_sequence
+      - exec: $forward_local
       - matches: "!resp_ip $geoip_cn"
         exec: drop_resp
 
-  - tag: query_is_remote
-    type: sequence
-    args:
-      - exec: $remote_sequence
-
   - tag: fallback
     type: fallback
     args:
-      primary: query_is_local_ip
-      secondary: query_is_remote
+      primary: query_is_non_local_ip
+      secondary: forward_remote_upstream
       threshold: 500
       always_standby: true
 
+  - tag: apple_domain_fallback
+    type: fallback
+    args:
+      primary: query_is_non_local_ip
+      secondary: forward_xinfeng_udp
+      threshold: 100
+      always_standby: true
+
   - tag: query_is_apple_domain
     type: sequence
     args:
       - matches: "!qname $geosite_apple"
         exec: return
-      - exec: $forward_local
-      - matches: "!resp_ip $geoip_cn"
-        exec: drop_resp
-      - matches: "!has_resp"
-        exec: $forward_xinfeng_udp
+      - exec: $apple_domain_fallback
 
   - tag: query_is_ddns_domain
     type: sequence
     args:
       - matches: qname $ddnslist
-        exec: $local_sequence
+        exec: $forward_local
 
   - tag: query_is_local_domain
     type: sequence
     args:
       - matches: qname $geosite_cn
-        exec: $local_sequence
+        exec: $forward_local
 
   - tag: query_is_no_local_domain
     type: sequence
     args:
       - matches: qname $geosite_no_cn
-        exec: $remote_sequence
+        exec: $forward_remote_upstream
 
   - tag: query_is_whitelist_domain
     type: sequence
     args:
       - matches: qname $whitelist
-        exec: $local_sequence
+        exec: $forward_local
 
   - tag: query_is_greylist_domain
     type: sequence
     args:
       - matches: qname $greylist
-        exec: $remote_sequence
+        exec: $forward_remote_upstream
 
   - tag: query_is_reject_domain
     type: sequence