RFR: 8341513: Remove the unused thread_type field from OSThread

[Stefan Karlsson]

On Wed, 16 Oct 2024 10:05:25 GMT, Amit Kumar <amitkumar at openjdk.org> wrote:

> This trivial PR cleans up ` thread_type` field. 
> 
> Build is fine on s390x-linux. I have tested on local system Mac-M1 but it failed due to this issue: [JDK-8340341](https://bugs.openjdk.org/browse/JDK-8340341)

Looks good to me. @dholmes-ora did some digging into the history of this, and it would be good to get his review on this change as well.

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Marked as reviewed by stefank (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/21532#pullrequestreview-2374341444