Migrate project-level Gradle build script to Kotlin DSL

[thunderbiscuit]

Description

Migrating the Gradle build scripts to Kotlin DSL.

Fixes #9

Notes to the reviewers

I have not tested the publishing workflow.

All Submissions:

• I've signed all my commits

[thunderbiscuit]

I have migrated all 3 build scripts. A few notes:

1. I'm keen on Gradle and over time I want to make sure I understand all our plugins and the configurations we use, as well as how we can make our build scripts better. This PR however is just a straight port of the Groovy DSL scripts.
2. I removed the withJavadocJar() config in the jvm build file because it currently only produced an empty jar.
3. I have not tested the nexus publishing task, but I did test the publishToLocalMaven task for the Android library and it worked well.
4. @notmandatory can I ask how you currently pass the username and password through the findProperty() method? I just want to make sure I find it using my val ossrhUsername: String? by project line. (aka is it defined in your home gradle.properties, or as a environment variable, or passed as a command line argument? Reading the docs I think it could come from many places. In any case I do think my line should pick it up, but let me know if it's not working and I can adjust. I'm also looking at this article to try and figure out how to do it best.

[notmandatory]

I'm currently using gradle.properties to get the publishing authentication info. Some more details here: https://github.com/bitcoindevkit/bdk-kotlin#how-to-publish

[thunderbiscuit]

The face when you realize your question is answered right there in the readme and now everyone knows you didn't read it meticulously:

I have tested in a local repo and indeed the current code will fetch the username and password correctly from global properties. I'll mark this PR as ready for review.

[notmandatory]

I merged the two pending PRs so now this one needs a rebase. Then I'll give it a test and otherwise LGTM.

[thunderbiscuit]

It was a weird rebase but I think I got it. The issue was that you had made changes to files I had deleted, so I just needed to delete them again.

[notmandatory]

For some reason I had to add this dependency for the ./gradlew :jvm:test command to work.

[thunderbiscuit]

Same with the migration to the new API! This PR was initially made against the older version of bdk-ffi and so it was working, but when I worked on updating the tests in a different PR I also found I needed to add this junit-vintage-engine. Thanks for fixing!

[notmandatory]

ACK 933af8c

I tested a staging publish and it worked so a full (non-test) publish should work too.