Add androidNative targets + test plugin

[natario1]

See discussion: #122 (comment)

To run tests,

• set either $ANDROID_HOME or multiplatformTesting.androidTools.sdkHome to the Android SDK directory or, if not installed, to some directory where the plugin can download them
• run ./gradlew atomicfu:runAllAndroidNativeTests

Testing plugin readme: https://github.com/deepmedia/multiplatform-testing/blob/main/readme.md

[natario1]

Hi @mvicsokolova , while still hoping that this gets merged soon (I am happy to provide any support)...

Is it OK for you if I publish these artifacts myself in Maven Central, with slightly different coordinates (like my.company.org.jetbrains.kotlinx:atomicfu instead of org.jetbrains.kotlinx:atomicfu)?

The difference would be that my publication would have Android Native targets, while yours hasn't. Then I can do the same for coroutines and write a simple gradle plugin for dependency substitution for end users. From my understanding, the license allows this, but it would be nice to have your approval, even if informally.

[roy-shchory]

What about arm 32 😍

[natario1]

Arm32 can be added after Kotlin 1.6.20, which contains an important fix for 32bit atomics.

[mvicsokolova]

We postpone the support of android native targets till the guarantees are published for them.
Please see #122 comment

[qwwdfsad]

Superseded with #275