Migrate all Java/Hamcrest tests to Kotlin/AssertK

[jamesonwilliams]

Contributor checklist

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

• MacBook, to run unit tests

• 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

I'm working towards removing Hamcrest from the project, and replacing it with AssertK. Likewise, I've been working on migrating all of the Java tests to Kotlin.

The goal of this current PR is to:

• Find any/all Java tests mentioning hamcrest
• Convert them to Kotlin & clean them up
• Replace their use of Hamcrest with AssertK

To find them, I did:

rg -i hamcrest $(git ls-files "*.java")

These were the tests that met those conditions:

1. app/src/test/java/org/thoughtcrime/securesms/contacts/SelectedContactSetTest.kt
2. app/src/test/java/org/thoughtcrime/securesms/groups/v2/ProfileKeySetTest.kt
3. app/src/test/java/org/thoughtcrime/securesms/groups/v2/processing/GroupStatePatcherTest.kt
4. app/src/test/java/org/thoughtcrime/securesms/groups/v2/processing/StateChainTest.kt
5. app/src/test/java/org/thoughtcrime/securesms/l10n/SupportArticleTest.kt
6. app/src/test/java/org/thoughtcrime/securesms/recipients/RecipientIdSerializationTest.kt
7. app/src/test/java/org/thoughtcrime/securesms/service/webrtc/collections/ParticipantCollectionTest.kt
8. libsignal-service/src/test/java/org/whispersystems/signalservice/api/groupsv2/DecryptedGroupUtilTest.kt
9. libsignal-service/src/test/java/org/whispersystems/signalservice/api/groupsv2/GroupsV2Operations_ban_Test.kt

After the changes, I validated that ./gradlew qa is still passing:

$ ./gradlew qa 
[...snip...]

And that there are no longer any files that match the search:

$ rg -i hamcrest $(git ls-files "*.java") | wc -l 
       0

[greyson-signal]

Awesome, thank you! Will go out in 7.30