RFR: 8290324: Move atomic operations outside of os_xxx.hpp [v4]

[Kim Barrett]

On Wed, 20 Jul 2022 23:41:08 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> The os_xxx.hpp files inject extra methods/fields that are specific to atomic operations into the `os` class. However, the injected methods/fields are used only by a specific os/cpu combination. Therefore, they should not be inside the `os` class, which should contain only APIs that are used across platforms.
>> 
>> - For ports where the `atomic_copy64()` function is used in a single file, I moved it as an inline function in that file
>> - Otherwise it's moved to `atomic_<os>_<cpu>.hpp`
>> - The linux/arm port is a little more involved, but the new code should be a little cleaner than the old code.
>
> Ioi Lam has updated the pull request incrementally with one additional commit since the last revision:
> 
>   moved 'static inline void atomic_copy64' outside of 'extern "C"' block

Marked as reviewed by kbarrett (Reviewer).

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PR: https://git.openjdk.org/jdk/pull/9501