Refactor build and publishing setup

[theimpulson]

Summary

This PR:

• Migrates build DSL to Kotlin as it has better syntax, highlights and lint support compared to groovy
• Switches to build version catalog to manage dependencies version across all modules in one place
• Relocates all publishing and test steps to extractor module
• Adds missing information for publishing extractor on mavencentral

Due diligence

• I carefully read the contribution guidelines and agree to them.
• I have tested the API against NewPipe.
• I agree to create a pull request for NewPipe as soon as possible to make it compatible with the changed API.

[TobiGr]

I went through the changes, but did not test them.

[theimpulson]

Signing support is still missing as that's needed for mavencentral

[theimpulson]

I couldn't find classes from the timeago-* modules in the currently generated jar file for the extractor nor do they seem to be getting generated separately or consumed in the NewPipe app. This made me assume that they are supposed to be consumed by the extractor and aren't supposed to be released.

Hence, I moved the javadoc, source and publishing setup to the extractor module.

[Stypox]

Thanks! I compared all of the files and they mostly look good to me. I also tried building locally and I was able to run tests, and also to build NewPipe when depending on the local copy of NewPipeExtractor.

I couldn't find classes from the timeago-* modules in the currently generated jar file for the extractor nor do they seem to be getting generated separately or consumed in the NewPipe app. This made me assume that they are supposed to be consumed by the extractor and aren't supposed to be released.

You mean that the timeago-parser JAR is not needed externally? Yeah that's correct, timeago-parser is just a subproject used internally in NewPipeExtractor that shouldn't be published separately.

Signing support is still missing as that's needed for mavencentral

I think it's fine to proceed with this using environment variables. Then we can setup a CI action that creates a new release on mavencentral. However this should be done in a separate PR

[theimpulson]

Signing support is still missing as that's needed for mavencentral

I will do this in a separate PR