Rework Gradle setup

[serras]

IMPORTANT: do not merge this PR if #3577 is going to be merged!!!!

This moves almost every configuration to the convention plug-in, so that subprojects can simply do:

plugins {
  id("arrow.kotlin")
}

Apart from the additional uniformity across all projects, this PR also:

• Sets a minimum SDK of 21, as discussed in Latest version 2.0.1 adds new android.permission.READ_PHONE_STATE to client manifest #3574
• Uses the recommended kotlin("stdlib") syntax instead of having a separate dependency in the catalog (this ensures we always depend on the libraries from the corresponding Kotlin version)
• Moves AnimalSniffer configuration from its own file into the convention plug-in
• Adds Android tests to the CI pipeline

Fixes #3574

[github-actions]

Kover Report

Total Project Coverage	46.00%

[serras]

Closed in favor of #3577