RFR: 8254719: ZGC: Clean up includes [v2]

[Stefan Karlsson]

On Wed, 14 Oct 2020 10:42:26 GMT, Per Liden <pliden at openjdk.org> wrote:

>> I noticed quite a few includes in ZGC that are no longer needed and can be cleaned out. As a side-effect I noticed that
>> `stackWatermark.hpp` and `threadSMR.hpp` weren't self contained, so I had to fix that too.
>> Builds on all Oracle platforms.
>
> Per Liden has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Review stefank

Changes requested by stefank (Reviewer).

src/hotspot/share/gc/z/zVerify.cpp line 37:

> 35: #include "memory/iterator.inline.hpp"
> 36: #include "memory/resourceArea.hpp"
> 37: #include "runtime/frame.inline.hpp"

This file uses oopDesc::is_oop, so I think oops/oop.hpp should stay.

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PR: https://git.openjdk.java.net/jdk/pull/644