Update Android build config, compileSDK, AGP and Gradle versions

[vbuberen]

This PR updates the build config and does some other minor updates to modernise the setup.

The reason for that is that 3.5.0 of Android Gradle plugin (AGP) is really old as of today and soon there might be issues with building the project, like it currently is if some project tries to use latest Kotlin versions with some 3.x AGP.

Initially I wanted to update the project to use the latest Android Gradle plugin 8 and Gradle wrapper 8, but at the moment there are some issues with project sync on the latest stable Flutter (3.7.11). Thus, I moved to the latest versions before.
UPD: With 3.7.12 release of Flutter I could update to Gradle 8 as it is mentioned in release notes: https://github.com/flutter/flutter/wiki/Hotfixes-to-the-Stable-Channel#3712-apr-19-2023

Changes:

• Bumped AGP version to 8.0.0 for both the plugin and example app.
• Updated Gradle wrapper version to 8.0.2 for both the plugin and example app.
• Bumped compileSDK to 33.
• Added namespace property to build.gradle files for compatibility with Gradle 8.
• Bumped Java to 17 in compile options to use the latest tooling and compatibility with Gradle 8.
• Dropped enableJetifier as project uses no support libraries and this property slows down builds.
• Did minor code cleanup with removing some deprecated properties and formatting.

P.S. Thanks for this useful package.

[ajinasokan]

Awesome! I will check it out in the evening.

[ajinasokan]

Available in v0.6.0