Update lintchecks module: migrate to KTS and fix tests

[valldrac]

Description

While adding some extra lint checks, I noticed that parts of the lintchecks module were a bit outdated. This PR makes a few minor changes, hopefully saving some maintenance time to your team.

Thanks for the continued work on Signal. Happy to contribute!

Summary of changes

• Migrate build script to Kotlin.
• Update lint version to 31.4.0 to align with the current AGP version (Google's recommendation found here).
• Fix broken unit tests in CardViewDetectorTest and LogDetectorTest.

Adding the lintchecks:test gradle task to the qa task could be a good idea too, to keep the tests updated.

[greyson-signal]

Thank you very much! This will go out in 7.24 :)