[WPPG] Separate files of overriding for building different variant

We moved the files in ThemePicker that are NOT shared with WPPG to
another folder.

Bug: 239542256
Test: Tested wallpaperpicker2Debug, themepickerDebug and googleDebug
could build

Change-Id: Ie90fcc0d614b10928bc948c03decc0d83d47f80e
diff --git a/Android.bp b/Android.bp
index c85fd2b..5b16e07 100644
--- a/Android.bp
+++ b/Android.bp
@@ -54,7 +54,7 @@
     name: "ThemePicker_res",
     tools: ["soong_zip"],
     srcs: [
-        "res/**/*"
+        "res/**/*",
     ],
     out: ["ThemePicker_res.zip"],
     cmd: "INPUTS=($(in)) && "
@@ -89,6 +89,10 @@
         "src_override/**/*.kt",
     ],
 
+    resource_dirs: [
+        "res_override",
+    ],
+
     use_embedded_native_libs: true,
 
     resource_zips: [":WallpaperPicker2_res", ":ThemePicker_res"],