Upgrade to Gradle 8.2 with kotlin DSL

[LZRS]

IMPORTANT: Where possible all PRs must be linked to a Github issue

• Upgrades gradle to v8.2.2
• Moves to Kotlin DSL for gradle
• Moves to using buildSrc for custom plugin build scripts
• Deletes subprojects anc and eir
• Updates spotless to v6.25.0

Checklist

• I have written Unit tests for any new feature(s) and edge cases for bug fixes
• I have added any strings visible on UI components to the strings.xml file
• I have updated the CHANGELOG.md file for any notable changes to the codebase
• I have run ./gradlew spotlessApply and ./gradlew spotlessCheck to check my code follows the project's style guide
• I have built and run the fhircore app to verify my change fixes the issue and/or does not break the app