Improve the speed of the Java test suite

[dmikusa]

Describe the Enhancement

Right now, it takes a very long time for the Java test suite to run, over 30 minutes. This makes running tests painful and slow. We should take some steps to improve the speed of it.

Possible Solution

I think there are a couple of easy wins to improve the speed of the Java test suite.

1. Right now we are testing against all three stacks: full, base and tiny. Most people are using either base or tiny, so we should drop testing on full. Java cares very little about the stack, so we should be safe dropping full.
2. Split Java test suites into smaller chunks and organize them into sub directories. By doing this, we can run smaller, lighter test suites that will complete faster. I'd be OK having a test suite per sample, but if there is some other logical grouping that splits them up into smaller chunks I'd be OK with that too.

Motivation

Making the test suite run faster makes it easier to validate changes and less effort to merge in things like updates.