Migrate buildSrc to composite build

[Goooler]

Ref detekt/detekt#4090

https://docs.gradle.org/7.5.1/userguide/composite_builds.html

[IgnatBeresnev]

Sorry it took so long to get to, I'm learning Gradle from your PRs and had to read up on it :)

Overall looks good and useful, I only have minor comments/questions

[IgnatBeresnev]

Awesome, thanks!

I noticed that #2704 is very related and it should hopefully make the BuildLogic class unnecessary. However, because it has more changes, it'll be more difficult to rebase than this PR, which mostly contains moved classes.

So if you don't mind, let's wait for #2704 to be merged first, and then hopefully it'll be easy for you to rebase onto it and just move all new/old classes without having to deal with line by line merge conflicts

[Goooler]

No problem.

[Goooler]

Maybe we no need this anymore once #2860 is merged, see https://docs.gradle.org/8.0/release-notes.html#improvements-for-buildsrc-builds.

[3flex]

Maybe we no need this anymore

It's still required. None of the improvements in Gradle 8 change the fact that buildSrc changes cause the whole project to become out of date - there's still a warning about this in the latest Gradle docs.

[Goooler]

Yeah, this PR will go on after #2704 merged.

[IgnatBeresnev]

#2704 has finally been merged :) Could you please rebase onto master or merge it in? I'll have a look right away

Since we utilize convention plugins, class BuildLogic : Plugin<Project> won't be needed anymore, right?

[Goooler]

Addressed to #2912.