RFR: 8367576: JvmtiThreadState::_debuggable is unused

[Albert Mingkun Yang]

On Fri, 12 Sep 2025 21:28:41 GMT, Francesco Andreuzzi <fandreuzzi at openjdk.org> wrote:

> The flag has been there since 8153779ad32d1e8ddd37ced826c76c7aafc61894, but seems to be unused.
> 
> Testing: `tier1`.

Marked as reviewed by ayang (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/27265#pullrequestreview-3220782480