RFR(M): 8200126: [TESTBUG] Open source VM runtime signal tests

[Mikhailo Seledtsov]

Please review: open sourcing vm signal tests.

     JBS: https://bugs.openjdk.java.net/browse/JDK-8200126
     Webrev: http://cr.openjdk.java.net/~mseledtsov/8200126.00.open/
     Testing:
         1. Linux-x64:
            make run-test TEST=hotspot_signal
            All tests PASS
         2. Multi-platform automated testing: Linux-x64, Win-x64, MAC
            hotspot_signal, hs-tier1, hs-tier2 - in progress

Thank you,
Misha