RFR: 8301578: Perform output outside synchronization in Module.class [v3]

[Per Minborg]

On Wed, 1 Feb 2023 08:51:16 GMT, Per Minborg <pminborg at openjdk.org> wrote:

>> This PR proposed to reduce contention in synchronized methods mainly by doing I/O operations outside synch blocks.
>
> Per Minborg has updated the pull request incrementally with three additional commits since the last revision:
> 
>  - Revert benchmark change
>  - Fix typo
>  - Use another type of comment

By putting `Unsafe` in an inner class, we are able to avoid circular initializer dependencies and I have been able to rewrite  `enableNativeAccess` access so it is completely lock-free.

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PR: https://git.openjdk.org/jdk/pull/12193