android: migrate app build system to use gradle

Most of the Android specific meson code has been removed and replaced with
the grade build system.

The new meson build scripts build and move the libmpd.so binaries into the correct
location that gradle expects. After than gradle handles building the rest of the Android app.

Icons and banners have been updated for the modern app packaging expectations.

For reference here was the figma template Google provides that I used to back the png versions
for older versions of Android <https://www.figma.com/community/file/1283953738855070149>

doc/user.rst

@@ -203,10 +203,8 @@ You need:
 * cmake
 * pkg-config
 * quilt
-* imagemagick
 * zip
 * libtool
-* rsvg-convert 
 * python 3.9+
 
 Just like with the native build, unpack the :program:`MPD` source
@@ -221,7 +219,8 @@ tarball and change into the directory.  Then, instead of
    --buildtype=debugoptimized -Db_ndebug=true \
    -Dwrap_mode=forcefallback \
    -Dandroid_debug_keystore=$HOME/.android/debug.keystore
- ninja android/apk/mpd-debug.apk
+ cd ../../android
+ ./gradlew assembleDebug
 
 :envvar:`SDK_PATH` is the absolute path where you installed the
 Android SDK; :envvar:`NDK_PATH` is the Android NDK installation path;