RFR (M): 8054819: Rename HeapRegionSeq to HeapRegionManager

[Thomas Schatzl]

Hi all,

  can I have reviews for the following change that renames HeapRegionSeq
to HeapRegionManager?

The reason is that after recent changes HeapRegionSeq got many new
responsibilities. It is not a straight sequence of heap regions any more
at all.

It's a straight rename of the class, moving into new files, and changing
"hrs"-prefixes to "hrm"-prefix.

Further the same change is done to the SA-agent.

CR:
https://bugs.openjdk.java.net/browse/JDK-8054819
Webrev:
http://cr.openjdk.java.net/~tschatzl/8054819/webrev/
Testing:
jprt, vm.heapdump (SA-agent tests), vm.gc tests on aurora

Thanks,
  Thomas