To improve support for Gradle's configuration cache, we need to stop
using the getProject() method at execution time. We can replace this
with other interfaces that Gradle provides, so no harm here.

This does not fully address configuration cache support, but is the
first step.

Related issues:

Contributor Checklist

• Review Contributing Guidelines.
• Commits contain discrete changes, messages include context about why the change was made and reference the relevant issues.
• Commit messages should be prefixed with one of the following (these are used to determine the next version we release):
  • patch: if the change added no new functionality and is backwards compatible
  • minor: if the change added new functionality and is backwards compatible
  • major: if the change is not backwards compatible
  • chore: if the change doesn't affect plugin logic/behavior at all (and obviously still backwards compatible)
  • Any of these can optionally specify an area of the plugin they affected in parentheses (e.g. patch(clojurescript): )
    • build
    • docs
    • clojure
    • clojurescript
    • common
    • repl
• Provide functional tests. (under clojurephant-plugin/src/compatTest)
• Update documentation for user-facing changes. (under docs/)
• Ensure all verification tasks pass locally. (./gradlew check)
• Ensure CI builds pass on all Java versions. (watch the checks tab once the PR is opened)

TIP: If troubleshooting a CI failure, look for the build scan URL in the workflow run summary.