Experiment with Jetty in place of Tomcat

[earldouglas]

Let's see if we can replace Tomcat with Jetty.

• Swap out com.heroku:webapp-runner for org.eclipse.jetty.ee10:jetty-ee10-webapp
• Launch Jetty via org.eclipse.jetty.ee10.runner.Runner

This will mostly be a drop-in replacement for WarPackageRunnerPlugin, but WebappComponentsRunnerPlugin is going to need its own version of com.earldouglas:webapp-components-runner.

For context, see scalatra/scalatra.g8#131 (comment)

See also:

• https://javadoc.jetty.org/jetty-12/org/eclipse/jetty/ee10/runner/Runner.html
• https://github.com/jetty/jetty.project/blob/jetty-12.0.x/jetty-ee10/jetty-ee10-runner/src/main/java/org/eclipse/jetty/ee10/runner/Runner.java