Componentize chrome/browser/ui/performance_controls (3/3)

This CL finishes the componentization of the aforementioned directory,
by moving the build of all tests - namely unit_tests, browser_tests and
test_support GN targets.
It also takes the opportunity to delete some TODOs.

No behavior change intended.

R=dljames@chromium.org

Bug: 428666921
Change-Id: I28c2eb1bdb0b4fed57caae3ecc7dbe596b26d279
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6696848
Commit-Queue: Antonio Gomes <tonikitoo@igalia.com>
Reviewed-by: Darryl James <dljames@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1481341}