Remove most examples

Most of the examples weren't strictly just demonstrating how to use the
android-activity API - rather they demonstrated using other libraries
in conjunction with android-activity.

Most of the examples have now been split into a standalone repository
under: https://github.com/rust-mobile/rust-android-examples

The na-mainloop and agdk-mainloop examples have been kept here since
they can be built against the local/in-tree version of android-activity
and are useful to keep for CI purposes.

This also runs `cargo update` for the na-mainloop and agdk-mainloop.

.github/workflows/ci.yml

@@ -89,28 +89,6 @@ jobs:
           -t x86
           -o app/src/main/jniLibs/ -- build
 
-      - name: Build agdk-egui example
-        if: matrix.rust_version == 'stable'
-        working-directory: examples/agdk-egui
-        run: >
-          cargo ndk
-          -t arm64-v8a
-          -t armeabi-v7a
-          -t x86_64
-          -t x86
-          -o app/src/main/jniLibs/ -- build
-
-      - name: Build agdk-eframe example
-        if: matrix.rust_version == 'stable'
-        working-directory: examples/agdk-eframe
-        run: >
-          cargo ndk
-          -t arm64-v8a
-          -t armeabi-v7a
-          -t x86_64
-          -t x86
-          -o app/src/main/jniLibs/ -- build
-
       - name: Documentation
         run: >
           cargo ndk -t arm64-v8a doc --no-deps
@@ -131,6 +109,10 @@ jobs:
         run: cargo fmt --all -- --check
         working-directory: android-activity
 
-      - name: Format agdk-egui example
+      - name: Format na-mainloop example
         run: cargo fmt --all -- --check
-        working-directory: examples/agdk-egui
+        working-directory: examples/na-mainloop
+
+      - name: Format agdk-mainloop example
+        run: cargo fmt --all -- --check
+        working-directory: examples/agdk-mainloop