Change the java API so a global default host allocator can be set.

[revans2]

Description

Originally the design for host memory limits wanted to give us the ability to do different things for different operations. That changed and now we really just want to set a global allocator instead.

In addition this removed host memory reservations, which was part of the original design, but is no longer needed and would be hard to maintain. It also adds in a Raw allocation API so that we can wrap the original allocation API if needed.

Note that this is a braking change not only because it is removing some unused features but it changes some APIs that some downstream projects are using, which will require the downstream project to have a patch ready to go to avoid breaking.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[jbrennan333]

These changes look good to me.

[vyasr]

@revans2 did this stall for any particular reason? Do we want to get this merged?

[revans2]

@vyasr It stalled because of other priorities, and this is not technically a requirement. I'll probably get back to it once all of the JSON work I am doing is done. If you want me to close it/retarget it to a different release I am happy to do it.

[vyasr]

No problem. We can keep it open if you plan to come back to it, and you can retarget it then. I just wanted to clean it up if it should be either merged soon or closed as a wontfix.