More robust nightly build

[m-reza-rahman]

Right now the project has a fairly basic nightly build: https://github.com/eclipse-ee4j/starter/blob/master/.github/workflows/nightly.yml.

It now does the following:

• Tests all the negative and positive cases for the Archetype
• Tests building using Maven
• Tests building via Docker

The nightly build can be further enhanced to add the following (in order of importance):

• Test the running generated project via Maven (e.g. start the application, call the REST endpoint, and stop the application)
• Test the running generated project via Docker
• Test the Starter UI (maybe via Playwright)

[m-reza-rahman]

The nightly build is getting quite lengthy. An easy fix would be splitting the archetype build into separate jobs by Java SE version. If someone wants to do a quick and easy PR for that, it would be a very helpful contribution.