RFR(S): 8076524: Remove jhat tests and help library from JDK

[Yekaterina Kantserova]

Hi,

Could I please have a review of this fix.

bug: https://bugs.openjdk.java.net/browse/JDK-8076524
webrev: http://cr.openjdk.java.net/~ykantser/8076524/webrev.00

This fix is a part of JEP 241: Remove the jhat Tool 
(https://bugs.openjdk.java.net/browse/JDK-8059039).

Thanks,
Katja