Convert some Java tests to Kotlin

[jamesonwilliams]

Contributor checklist

• I am following the Code Style Guidelines
• I have tested my contribution on these devices:

• This runs on the local host, not the device

• My contribution is fully baked and ready to be merged as is
• I ensure that all the open issues my contribution fixes are mentioned in the commit message of my first commit using the Fixes #1234 syntax

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Description

There's still quite a bit of Java left in the codebase. It probably makes sense to convert the low-risk stuff to Kotlin, first (e.g., sample apps, unit test files, etc.)

Here I just grabbed a random batch of test files that were still in Java and converted them to Kotlin. I started with Android Studio's "Convert Java to Kotlin..." utility and then applied some manual cleanups.

1. core-util-jvm/src/test/java/org/signal/core/util/logging/LogTest.kt
2. core-util/src/test/java/org/signal/core/util/BreakIteratorCompatTest.kt
3. core-util/src/test/java/org/signal/core/util/ListUtilTest.kt
4. core-util/src/test/java/org/signal/core/util/money/FiatMoneyTest.kt
5. device-transfer/lib/src/test/java/org/signal/devicetransfer/DeviceTransferAuthenticationTest.kt
6. device-transfer/lib/src/test/java/org/signal/devicetransfer/WifiDirectTest.kt
7. donations/app/src/main/java/org/signal/donations/app/MainActivity.kt
8. libsignal-service/src/test/java/org/whispersystems/util/FlagUtilTest.kt
9. paging/lib/src/test/java/org/signal/paging/DataStatusTest.kt

Test files are also good candidates to finish migrating because it's easy to verify that they still work or not:

./gradlew :core-util-jvm:test :device-transfer:test :donations:test :libsignal-service:test :paging:test

[greyson-signal]

Thank you! Always better to have more things moved over to kotlin, and I agree that tests are a great place to start.