Fix CI tests

[emakryo]

Hi,
I use this rust-android-gradle plugin in every project with Android and Rust. So I hope I can contribute to this plugin.

I noticed that the CI tests failed in my fork. There are two reasons for this:

• GitHub Actions' runner image update (NDKs)
• Rust compatibility to NDK has changed (announcement)

I fixed these problems by

• updating NDK versions used in the test and adding manual installation steps for old NDKs in the CI workflow
• adding rust channel (toolchain) configuration in tests depending on NDK versions

Also, I update several actions to erase workflow warnings.