RFR: 8373441: Remove DCmdFactory::_enabled

[Johan Sjölen]

On Fri, 12 Dec 2025 14:54:52 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> The `DCmdFactory::_enabled` is always set to `true` and there doesn't seem to be a reason to set it to `false`.
> 
> This PR removes this field and simplified the creation of `DCmdFactory` objects.
> 
> The related `_hidden` field is also currently not used, but may be used in the future when deprecating DCmds, so we leave it unchanged.
> 
> Note that now `jmm_GetDiagnosticCommandInfo()` always set `dcmdInfo::enabled` to `true` to be compatible with Java code.

Fine by me, thanks.

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Marked as reviewed by jsjolen (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/28794#pullrequestreview-3572462286