Use new soong support to install privapp xml

This allows better overriding of it in the variants of this apex
that have a different package name.

Bug: 242509786
Test: build google tethering, diff before & after
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:91442c93fb8d7f67bf90faab0552428ff07f0452)
Merged-In: I84c53458686f70408ec759df854f5fcdee9cdaed
Change-Id: I84c53458686f70408ec759df854f5fcdee9cdaed

Tethering/Android.bp

@@ -195,7 +195,7 @@ android_app {
     certificate: "networkstack",
     manifest: "AndroidManifest.xml",
     use_embedded_native_libs: true,
-    required: ["privapp_allowlist_com.android.tethering"],
+    privapp_allowlist: ":privapp_allowlist_com.android.tethering",
     apex_available: ["com.android.tethering"],
     lint: { strict_updatability_linting: true },
 }
@@ -211,7 +211,7 @@ android_app {
     certificate: "networkstack",
     manifest: "AndroidManifest.xml",
     use_embedded_native_libs: true,
-    required: ["privapp_allowlist_com.android.tethering"],
+    privapp_allowlist: ":privapp_allowlist_com.android.tethering",
     apex_available: ["com.android.tethering"],
     lint: { strict_updatability_linting: true },
 }

Tethering/apex/Android.bp

@@ -112,10 +112,7 @@ apex {
         "ServiceConnectivityResources",
         "HalfSheetUX",
     ],
-    prebuilts: [
-        "current_sdkinfo",
-        "privapp_allowlist_com.android.tethering",
-    ],
+    prebuilts: ["current_sdkinfo"],
     manifest: "manifest.json",
     key: "com.android.tethering.key",
     // Indicates that pre-installed version of this apex can be compressed.

Tethering/apex/permissions/Android.bp

@@ -19,10 +19,7 @@ package {
     default_visibility: ["//packages/modules/Connectivity/Tethering:__subpackages__"],
 }
 
-prebuilt_etc {
+filegroup {
     name: "privapp_allowlist_com.android.tethering",
-    sub_dir: "permissions",
-    filename: "permissions.xml",
-    src: "permissions.xml",
-    installable: false,
+    srcs: ["permissions.xml"],
 }