Android support

[marcprux]

This PR adds CI support for building and testing on Android using the swift-android-action. You can see a successful CI run at https://github.com/marcprux/Yams/actions

Everything build out of the box, but the measure function in PerformanceTests.swift needed to be disabled due to high emulator variance in tests (and the inability to configure the the maximum tolerated standard deviation on non-Darwin platforms; see swiftlang/swift-corelibs-xctest#506).

[lynchsft]

Hi Marc,

I'd love to add support for Swift on Android.

One ask please. Let's provide a more forward-looking bridge to better self.measure functionality on non-Darwin platforms.
Would you please:

1. implement a basic wall-clock duration calculation in the Android measure function and simply print the duration (formatted) to std out?
2. Add a url to your PR in corelibs-xctest to the comment in the Android measure function.

Thank you!

[marcprux]

OK, I've implemented this and made the comment. My output of the duration is just the TimeInterval, because that is how the standard XCTest measure function outputs it. E.g.:

Test Case '-[YamsTests.PerformanceTests testUsingSwiftDecodableWithUTF8]' measured [CPU Cycles, kC] average: 16242.921 …

[lynchsft]

The lint failed on your variable name t.
Also, thank you for the comment in the corelibs-xctest project. But actually I was intending to link the other direction: In the comment that starts // the hardwired max standard would you please add a URL to your proposed change in xctest. We'll want to track that effort over time to remove this workaround when possible.

Thank you!

[marcprux]

Ahh, understood. Both should be addressed now.

[lynchsft]

Alll checks pass! :)
This is a nominal approve ✅. Please update the changelog per the CONTRIBUTING guide. 🙏🏻

[marcprux]

Please update the changelog per the CONTRIBUTING guide.

Apologies for missing that. Done in 8366191.