Multiplatform: Port :zoomable module to Compose Multiplatform

[DSteve595]

#9

This adds a convention plugin for modules using Kotlin Multiplatform + Jetbrains Compose, and migrates the :zoomable module to use it.

Things to note:

• The Compose compiler plugin is set to the AndroidX one rather than the Jetbrains one. I'm not sure if that matters.
• AndroidX Compose libraries are still in libs.toml, but can (should) be removed once all modules are moved over.
• Migrated :zoomable's build.gradle to KTS, since the Jetbrains Compose Gradle plugin adds some useful dependency declarations.
• Only Android and Desktop targets are set up currently.
• I'm not sure if I'm setting -Xjvm-default=all properly.
• I migrated tests from Truth to kotlin.test, but that API is pretty basic. Now using assertk.

(This is a re-open of #10, which got lost when something weird happened to my fork)

[saket]

@DSteve595 can you rebase this PR? telephoto is now able to run screenshot tests in PRs too!

[emulator-wtf]

:zoomable-image:core - Tests were flaky!

✅ 119 passed / ⚠️ 1 flaky

First failure encountered:

me.saket.telephoto.zoomable.ZoomableImageTest.various_image_sizes_and_alignments[BottomCenter,Fill,SmallerThanLayoutSize,FillMaxSize,SubSamplingEnabled] click for details

androidx.compose.ui.test.ComposeTimeoutException: Condition still not satisfied after 5000 ms
at androidx.compose.ui.test.AndroidComposeUiTestEnvironment$AndroidComposeUiTestImpl.waitUntil(ComposeUiTest.android.kt:448)
at androidx.compose.ui.test.junit4.AndroidComposeTestRule.waitUntil(AndroidComposeTestRule.android.kt:306)
at me.saket.telephoto.util.WaitUntilKt.waitUntil-8Mi8wO0(waitUntil.kt:7)
at me.saket.telephoto.zoomable.ZoomableImageTest.various_image_sizes_and_alignments(ZoomableImageTest.kt:214)

---

There were more failures, click for details

• :zoomable-image:sub-sampling-image - test failures

[DSteve595]

@saket Done! Is that flaky test from my PR?

[saket]

Awesome! I don't think the flake was introduced here. I've been dealing with flakes for a while. They're proving really hard to solve.

[saket]

Huh, emulator-wtf is now saying one test failed despite posting a success message earlier. I'll rerun the tests.

cc @madisp

[saket]

Thanks Steve!

[madisp]

@saket hmm, I think this can happen if you have multiple modules and one of them succeeds at first (we don't know beforehand how many different module tests there can be so we can't really link them together like that) and another one fails later.

Ideally I'd like to figure out how to show GitHub checks for PR-triggered builds as well, that would have a stronger indication (you'd see some tests as running/queued first and you could make some set of checks as required via branch protection rules).

[saket]

@madisp Got it, thanks for explaining!