RFR: Rich assertion failure logging

[Aleksey Shipilev]

http://cr.openjdk.java.net/~shade/shenandoah/rich-asserts/webrev.01/

This reworks all the assorted in-line ASSERT blocks we have around Shenandoah code into the single
facility that prints everything it knows about the oop, fwdptr, regions, matrix, etc. The triggered
assert would print the rich message, like current Verifier does.

Testing: hotspot_gc_shenandoah {fastdebug|release}, injecting failures

Thanks,
-Aleksey