RFR(L) 8154154: Separate G1 specific policy code from the CollectorPolicy class hierarchy

[Mikael Gerdin]

Hi all,

Please review this change to split the class G1CollectorPolicy.

G1 has traditionally had all its policy related code in G1CollectorPolicy.
This is somewhat problematic since the JVM heap bootstrap process is 
designed to first create a CollectorPolicy and then pass that to the 
CollectedHeap constructor.
To make it easier to understand which parts of the G1 policy are related 
to pre-heap-initialization and which parts are related to the runtime 
policy decisions I suggest that this is broken up into two classes:
- G1CollectorPolicy which implements the CollectorPolicy interface
- G1Policy which contains the implementation of the runtime policy for 
the G1 collector.

While updating #includes to refer to the new file I've instead opted to 
remove them where there was in fact no reference to the G1 policy in the 
file.

Initialization:
In this change I've tried to keep the initialization sort of unchanged. 
The G1CollectedHeap constructor calls create_g1_policy() fairly early on 
in case some other objects depend on the policy object being available 
during initialization.
I did also take the opportunity to fix the initialization of 
G1CollectionSet to pass the policy object to its constructor.

Patch notes:
G1YoungGenSizer was slightly modified. Instead of having 
post_heap_initialize() figure out and set the MaxNewSize flag I've moved 
this to a method called from G1Policy::init(), at this point the 
max_young_length() can be safely determined and from what I can see 
nobody is expecting the value of the MaxNewSize to stay unchanged until 
the end of G1CollectedHeap::initialize()

Testing: RBT GC Testing, JPRT, Performance testing on aurora.
Bug: https://bugs.openjdk.java.net/browse/JDK-8154154
Webrev: http://cr.openjdk.java.net/~mgerdin/8154154/webrev.0/


Thanks
/Mikael