RFR: 8325517: Shenandoah: Reduce unnecessary includes from shenandoahControlThread.cpp

[Kelvin Nilsen]

On Thu, 8 Feb 2024 18:32:46 GMT, William Kemper <wkemper at openjdk.org> wrote:

> The control thread used to run much more of the cycle directly. This code was all factored out into different classes, but many of the vestigial headers remained. Removing these improves compilation times and makes maintenance easier.

Marked as reviewed by kdnilsen (no project role).

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PR Review: https://git.openjdk.org/jdk/pull/17778#pullrequestreview-1871214656