Update Gradle, build tools, libraries, demo code, tests

[nikclayton]

Build infrastructure

• Update Gradle to 8.1.1
• Update Android Gradle Plugin to 8.0.2
• Rewrite build.gradle files to avoid deprecated idioms
• Use maven-publish plugin instead of deprecated maven plugin

Language

• Update Kotlin to 1.8.22

Library code

• Update compileSdk and targetSdk to 33
• Update library dependencies to latest versions (at time of writing)
• Remove deprecated "package" from AndroidManifest.xml
• Add mandatory "namespace" declaration to build.gradle files

Demo app code

• Optimise imports
• Rewrite "switch" on resource IDs as "if" (resource IDs are non-final)

Tests

• Update deprecated method call, use the correct package name

[nikclayton]

Hi. In order to be able to debug https://github.com/penfeizhou/APNG4Android/issues/188 I need to be able to build the library locally.

I couldn't, using Android Studio Giraffe (the current stable version), so I updated Gradle and assorted libraries to get that to work.

This passes .\gradlew check connectedCheck, and the demo app builds and installs with no problems.

I have not tested the changes to the Maven publishing pipeline. The maven plugin is not supported any more. This uses the new plugin, but will need careful review to make sure it still does what you want.

[nikclayton]

Turned out that setting the root project name was needed as well.

With the changes in this PR I can take a project that uses APNG4Android and use a local copy by:

1. Checking out this repo (or a fork)
2. Editing my project's settings.gradle file, and adding:

   includeBuild('/path/to/my/checkout/of/APNG4Android')

3. Editing my project's dependencies and changing:

implementation 'com.github.penfeizhou.android.animation:glide-plugin:2.23.0'

to

implementation 'com.github.penfeizhou.android.animation:plugin_glide'

(i.e., drop the version number, and change glide-plugin to plugin_glide to match the module name).