Update all of the examples

[rib]

Since I was looking at hopefully spinning an android-activity release soon, I wanted to update these examples and also take the opportunity to test them against android-activity main.

For each example, this:

• Updates to using Android Gradle Plugin 8.0
• Adds ndkVersion to build.gradle
• Updates all cargo deps and fixes / updates examples as needed
• Avoids depending on any git branches for winit/egui now that the required Android support is upstream.
• Removes all .idea files and adds .idea to .gitignore

This also adds a na-egui example that tests NativeActivity + Egui (same code as agdk-egui, but built against NativeActivity instead of GameActivity)

This also fixes *-mainloop on newer versions of Android by posting dummy frames to unblock input.

Newer versions of Android will stop delivering input to applications that don't appear to be responsive because they aren't rendering anything. This updates na-mainloop and agdk-mainloop so that they at least do a NOOP post of an untouched framebuffer each frame, so that they continue to be delivered touch input.

.github/workflows/ci.yml has been updated to ensure all the examples are built now, and ./gradlew build is run, in addition to cargo ndk build