test: add TestConcoredockerApi covering read/write/unchanged/initVal

[avinxshKD]

closes #464

Added TestConcoredockerApi.java... real file I/O tests for read(), write(), unchanged(), initVal() using temp dirs.

Had to add 5 package-level setters to concoredocker.java (setInPath, setOutPath, setDelay, getSimtime, resetState) so tests can wire up without touching /in /out.

Builds on top of #468 (methods are now public).

[avinxshKD]

@pradeeban TestConcoredockerApi: 20/20

TestLiteralEval: 50/50

[avinxshKD]

Hey @pradeeban Pls take a look, and one thing worth noting, setDelay(0) in the test runner is necessary, otherwise each read() blocks for 1s and the suite takes around 6s for nothing. let me know if you'd prefer a different approach there.

Took a bit longer than expected since I wanted to make sure the temp dir setup was clean and didn't bleed state between tests, resetState() handles that :p

[avinxshKD]

@pradeeban also Python ZMQ uses send_json/recv_json but Java sends Python literals.... True/None will break json.loads on the Python side. worth aligning? for Java I think,

just want to make sure its a ryt direction :)

[pradeeban]

Yes, pls align with Python implementation. Like I mentioned a few times in different places, Java implementation was done without much thought. So, if you find some misalignment with Python implementation, it was simply an oversight.