Introduce ThreadType::kInteractive

This adds a new ThreadType kInteractive. This is a no-op and is the
first step of the scenario-based priority tuning work.

Bug: 423313079
Change-Id: I0f391e4609b68e39fdc97e3d398f95100122ea47
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6419127
Reviewed-by: Etienne Pierre-Doray <etiennep@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Matthew Denton <mpdenton@chromium.org>
Reviewed-by: Andrea Orru <andreaorru@chromium.org>
Commit-Queue: Jiahe Zhang <jiahe.zhang@intel.com>
Reviewed-by: Francois Pierre Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1472279}