RFR: 8238174: migrate ObjectMonitor::_owner field away from C++ volatile semantics

[Daniel D.Daugherty]

On Tue, 17 Nov 2020 22:44:11 GMT, Daniel D. Daugherty <dcubed at openjdk.org> wrote:

> Drop volatile from the ObjectMonitor::_owner field. Update all naked
> field loads to use the new owner_raw() accessor or the existing
> owner_is_DEFLATER_MARKER() accessor.

Gory details and background:

Note: Previous work updated the setters to use appropriate Atomic operations:

     JDK-8236035 refactor ObjectMonitor::set_owner() and _owner field setting

Note: Previous work also updated the owner() accessor to check for the
DEFLATER_MARKER value and return NULL. Those existing calls to owner()
did not need to know about the DEFLATER_MARKER value so we hid it from
those code sites.

To verify that all uses of ObjectMonitor::_owner were found and converted,
I temporarily changed the `_owner` field to `_ownerX` and updated the
expected `_owner` field uses to `_ownerX`. The resulting JDK built in
release, fastdebug and slowdebug configs.

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PR: https://git.openjdk.java.net/jdk/pull/1278