feat(coverage): Demangling of Java function names in coverage results

[vogelsgesang]

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This commit adds demangling support for Java. I couldn't find any good third-party library for this, so I quickly implemented my own, based on https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.3.2

It might still be have a couple of bugs, but at least for my simple smoke tests, demangling seems to work just fine.

Works towards #362