Add experimental MPV player backend (#161)

Experimental MPV player backend

Related to #14, #22, & #85

You can switch to MPV in advanced settings and toggle using hardware
decoding or not.

This uses code and buildscripts from
https://github.com/mpv-android/mpv-android, plus other third party
libraries to build MPV

build_ffmpeg_decoder.sh

@@ -1,57 +0,0 @@
-#!/usr/bin/env bash
-set -ex
-
-if [ -z "$1" ]; then
-  echo "Error: Must provide NDK path"
-  exit 1
-fi
-NDK_PATH="$1"
-
-# Config
-ANDROID_ABI=21
-ENABLED_DECODERS=(dca ac3 eac3 mlp truehd)
-FFMPEG_BRANCH="release/6.0"
-
-# Path configs
-DIR_PATH="$(pwd)"
-TARGET_PATH="$DIR_PATH/app/libs"
-MEDIA_PATH="$DIR_PATH//ffmpeg_decoder/media"
-FFMPEG_MODULE_PATH="$MEDIA_PATH/libraries/decoder_ffmpeg/src/main"
-FFMPEG_PATH="$DIR_PATH/ffmpeg_decoder/ffmpeg"
-HOST="$(uname -s | tr '[:upper:]' '[:lower:]')"
-HOST_PLATFORM="$HOST-x86_64"
-
-mkdir -p "$TARGET_PATH"
-mkdir -p ffmpeg_decoder
-
-media_version="$(grep "androidx-media3 = " gradle/libs.versions.toml | awk -F'"' '{print $2}')"
-
-pushd ffmpeg_decoder || exit
-
-if [[ -d media ]]; then
-  pushd media || exit
-  git checkout --force "$media_version"
-else
-  git clone https://github.com/androidx/media.git --depth 1 --single-branch -b "$media_version" media
-fi
-
-if [[ -d ffmpeg ]]; then
-  pushd ffmpeg || exit
-  git checkout --force "$FFMPEG_BRANCH"
-else
-  git clone https://github.com/FFmpeg/FFmpeg --depth 1 --single-branch -b "$FFMPEG_BRANCH" ffmpeg
-fi
-
-ln -s "$FFMPEG_PATH" "${FFMPEG_MODULE_PATH}/jni/ffmpeg"
-
-pushd "${FFMPEG_MODULE_PATH}/jni" || exit
-
-./build_ffmpeg.sh "${FFMPEG_MODULE_PATH}" "${NDK_PATH}" "${HOST_PLATFORM}" "${ANDROID_ABI}" "${ENABLED_DECODERS[@]}"
-
-pushd "$MEDIA_PATH" || exit
-./gradlew :lib-decoder-ffmpeg:assemble
-popd || exit
-
-popd || exit
-cp "$MEDIA_PATH/libraries/decoder_ffmpeg/buildout/outputs/aar/lib-decoder-ffmpeg-release.aar" "$TARGET_PATH/"
-popd || exit