2.1.0

Update workflows, dependencies, and configurations:

- Free up disk space in CI workflows using jlumbroso/free-disk-space@v1.3.1.
- Enable read-only Gradle caching and adjust task dependencies.
- Add `codecov.yml` for coverage reporting.
- Update Qodana linter version and JDK to 21 in `qodana.yml`.
- Remove `pluginUntilBuild` and introduce `platformBundledModules` property in Gradle.
- Update plugin metadata in `plugin.xml` to version 2.1.0 and add resource-bundle entry.
- Refactor release asset creation logic to streamline handling of changelogs and releases.
- Fix licensing comments and adjust Gradle wrapper scripts.
- Ignore `.DS_Store` and minor content fixes in `.gitignore`.