Our prior approach of adding all main/test source dirs to the dev source
set, caused Eclipse to add them as duplicate entries in its classpath
config. We now instead keep them separate, but add the main/test source
dirs to the runtime classpath.

There were also some dummy entries for "libraries" of the clojurescript
compiled output, which are now detected as source entries by properly
switching them over to use allSource and set the output as a classes
dir.

This fixes #127

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.