Replace usage of `android_binary` with `build_test` for libraries

`android_binary` is only required when building an application.

PiperOrigin-RevId: 469413752

extensions/ffmpeg/src/main/AndroidManifest.xml

-<?xml version="1.0" encoding="utf-8"?>
-<!-- Copyright (C) 2016 The Android Open Source Project
-
-     Licensed under the Apache License, Version 2.0 (the "License");
-     you may not use this file except in compliance with the License.
-     You may obtain a copy of the License at
-
-          http://www.apache.org/licenses/LICENSE-2.0
-
-     Unless required by applicable law or agreed to in writing, software
-     distributed under the License is distributed on an "AS IS" BASIS,
-     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-     See the License for the specific language governing permissions and
-     limitations under the License.
--->
-
-<manifest package="com.google.android.exoplayer2.ext.ffmpeg">
-  <uses-sdk />
-</manifest>

extensions/flac/src/main/AndroidManifest.xml

-<?xml version="1.0" encoding="utf-8"?>
-<!-- Copyright (C) 2016 The Android Open Source Project
-
-     Licensed under the Apache License, Version 2.0 (the "License");
-     you may not use this file except in compliance with the License.
-     You may obtain a copy of the License at
-
-          http://www.apache.org/licenses/LICENSE-2.0
-
-     Unless required by applicable law or agreed to in writing, software
-     distributed under the License is distributed on an "AS IS" BASIS,
-     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-     See the License for the specific language governing permissions and
-     limitations under the License.
--->
-
-<manifest package="com.google.android.exoplayer2.ext.flac">
-  <uses-sdk />
-</manifest>

extensions/media2/src/main/AndroidManifest.xml

-<?xml version="1.0" encoding="utf-8"?>
-<!-- Copyright 2019 The Android Open Source Project
-
-     Licensed under the Apache License, Version 2.0 (the "License");
-     you may not use this file except in compliance with the License.
-     You may obtain a copy of the License at
-
-          http://www.apache.org/licenses/LICENSE-2.0
-
-     Unless required by applicable law or agreed to in writing, software
-     distributed under the License is distributed on an "AS IS" BASIS,
-     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-     See the License for the specific language governing permissions and
-     limitations under the License.
--->
-<manifest package="com.google.android.exoplayer2.ext.media2">
-  <uses-sdk />
-</manifest>

extensions/opus/src/main/AndroidManifest.xml

-<?xml version="1.0" encoding="utf-8"?>
-<!-- Copyright (C) 2016 The Android Open Source Project
-
-     Licensed under the Apache License, Version 2.0 (the "License");
-     you may not use this file except in compliance with the License.
-     You may obtain a copy of the License at
-
-          http://www.apache.org/licenses/LICENSE-2.0
-
-     Unless required by applicable law or agreed to in writing, software
-     distributed under the License is distributed on an "AS IS" BASIS,
-     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-     See the License for the specific language governing permissions and
-     limitations under the License.
--->
-
-<manifest package="com.google.android.exoplayer2.ext.opus">
-  <uses-sdk />
-</manifest>

extensions/vp9/src/main/AndroidManifest.xml

-<?xml version="1.0" encoding="utf-8"?>
-<!-- Copyright (C) 2016 The Android Open Source Project
-
-     Licensed under the Apache License, Version 2.0 (the "License");
-     you may not use this file except in compliance with the License.
-     You may obtain a copy of the License at
-
-          http://www.apache.org/licenses/LICENSE-2.0
-
-     Unless required by applicable law or agreed to in writing, software
-     distributed under the License is distributed on an "AS IS" BASIS,
-     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-     See the License for the specific language governing permissions and
-     limitations under the License.
--->
-
-<manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    package="com.google.android.exoplayer2.ext.vp9">
-
-  <uses-sdk />
-  <uses-feature android:glEsVersion="0x00020000"/>
-
-</manifest>