Update AGP, NDK, CMake, and other dependencies

[emrekultursay]

This PR modernizes all samples to use relatively newer versions for most major dependencies. It uses the following versions:

AGP=7.4.2
Gradle=7.5
NDK=r25c
CMake=3.22.1
minSdkVersion=26
compileSdkVersion/targetSdkVersion=34
ABIs=arm64,x86_64 only
Validation Layers prebuilts=1.3.290.0

Also slightly bumps appcompat and game-activity dependency versions.

This change also updates all README files, and the test matrix used to verify all 6 tutorials.

[spectecjr]

So generally LGTM, but I'm not sure if we need x86_64 to have a different target SDK version (31) or not. Currently it's set to 34 in every sample, which the README says we need for other targets.

Assuming that what is in the CL is correct, this is good to go. Approving, assuming we can circle back if necessary.

[emrekultursay]

Re-did testing on API level 34 with x86_64 emulator.