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

[William Kemper]

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.

I only removed a couple of headers that were obviously not needed directly in the control thread (I think there are a couple more I can trim). I didn't try to find and declare all the direct/first-level dependencies (`log.hpp`, for example).

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PR Comment: https://git.openjdk.org/jdk/pull/17778#issuecomment-1934831924