Update shadow jar plugin, and code cleanup

[Omico]

Please review each commit message for the details.

[MatkovIvan]

Combining cleanups and introducing new public API is not good idea.

PS I've assigned right people as reviewers

[terrakok]

Could you explain your motivation for refactorings and version updates?
I don't see a reason for that at all. Yes, might be it is not perfect but there is no reasons to change it right now.

[Omico]

Could you explain your motivation for refactorings and version updates? I don't see a reason for that at all. Yes, might be it is not perfect but there is no reasons to change it right now.

Just general code cleanup, I can revert it if you unhappy with that.

For our current Dependencies class, honestly I want to let it inherit org.gradle.api.plugins.ExtensionAware therefore we can enable the ability to let user do some customization. Thought this we can declare dependencies dynamically via Gradle API. What do you think of this idea? Here is an example that I'm using below:

https://github.com/Omico/picsum/blob/96cbfe231420c4951740313058962e252874dfb5/picsum/kami/kotlin-multiplatform-library/build.gradle.kts#L24-L37

https://github.com/Omico/picsum/blob/96cbfe231420c4951740313058962e252874dfb5/picsum/kami/android-application/build.gradle.kts#L23-L28

kami & kamiDependenciesexist to avoid potential naming restrictions of Gradle.

Also, the code above is generable via Kotlinpoet, but I don't have time to implement it because I have a full-time job.