RFR: 8303151: DCmd framework cleanups [v3]

[Yi Yang]

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On Sun, 5 Mar 2023 05:46:37 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Whilst working on the DCmd code I noticed two items that could be cleaned up:
>> 
>> 1. The `NMTDCmd` is registered after the call to `register_dcmds()` instead of inside it.
>> 
>> 2. The "extension" mechanism to define external DCmds (as added by [JDK-7132515](https://bugs.openjdk.org/browse/JDK-7132515) for `UnlockCommercialFeatures`) is no longer needed.
>> 
>> Testing: tiers 1-3
>> 
>> Thanks
>
> David Holmes has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Relocate regoster_dcmds to DCmd class and get rid of DCmdRegistrat class

Thanks for doing this. Looks good to me.

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Marked as reviewed by yyang (Committer).

PR: https://git.openjdk.org/jdk/pull/12847