Speedup Github Action runs

[poikilotherm]

Artifacts: Uploads are slow!

• Do not include the WAR file in the java-builddir.tar (140 MB)
• Maybe do not include the dataverse/WEB-INF/lib dir (160MB)

Caching:

• Analyse why there are 240 MB and 800 MB caches
• Do not use a cache for very different versions of the POM. We're stable enough, just make it one cache.
• Delete the cache at certain intervals (time based? closed PR based?)
• Optimize cache ignores, do not include installed build artifacts