Move checkJava logic into Java code

[tothtamas28]

When running kompile (and potentially other tools of the K toolkit), a script checkJava is run to check version compatibility of the installed JRE with K.

If possible (i.e. if each tool that runs checkJava eventually ends up running Java code), consider moving this logic into the Java code base, as introspecting the running JVM for its version is simpler and less error-prone than parsing version strings from diverse sources.

Related: #4059

[Baltoli]

The main reason that this logic lives in the Bash script is to avoid spinning up a JVM if Nailgun is running; we should perhaps just fix the string processing as a first pass at the issue.

This is pretty old code, and we should also take the opportunity to refactor the script if there are opportunities to do so.

[Baltoli]

We should make an effort to give a good message for Java >= 11; older versions we can just bail out. The reason for this is that from 8 -> 11 the version numbering scheme changed, and so our logic can be more consistent by only supporting one format.