fix(snap): Fix zenity part not buildable due to unavailable stage snap

The fixes the following build failure:

```text
Pulling zenity-integration
Error downloading snap 'zenity-integration' from channel 'latest/stable'.
```

This is due to the fact that the snap is based on core22, but [the zenity-integration stage snap only supports core18](https://forum.snapcraft.io/t/the-zenity-integration-stage-snap/10870):

```text
$ snap info zenity-integration --verbose | grep ^base:
base:    core18
```

We should fall back to [the generic approach](https://forum.snapcraft.io/t/support-presenting-gui-dialogs-using-zenity/41218) until the situation is improved.

Fixes #12.

Signed-off-by: 林博仁(Buo-ren Lin) <buo.ren.lin@gmail.com>

Author: brlin-tw

snap/snapcraft.yaml

@@ -125,10 +125,14 @@ parts:
 
   # Integrate custom dialogs in your snap - doc - snapcraft.io
   # https://forum.snapcraft.io/t/integrate-custom-dialogs-in-your-snap/10825
-  zenity-integration:
+  zenity:
     plugin: nil
-    stage-snaps:
-      - zenity-integration
+    stage-packages:
+      - zenity
+    prime:
+      - usr/bin/zenity
+      - usr/share/zenity/*
+      - usr/share/doc/*/copyright*
 
   main:
     after:
@@ -163,6 +167,11 @@ parts:
 
       "${CRAFT_PROJECT_DIR}/snap/local/patching/patch-desktop-entries.bash"
 
+layout:
+  # Fix resource relocation problem of zenity part
+  /usr/share/zenity:
+    symlink: $SNAP/usr/share/zenity
+
 # Apps that are exposed by the snap package
 # If the _app_name_ is identical with the _snap_name_ it can be directly
 # run with `_snap_name_` or `snap run _snap_name_` commands, otherwise it