Move ContentScriptMatchingBrowserTest to browser_tests

From its old home of from extensions_browsertests. This test covers
interaction of content scripts, frame trees and ScriptInjectionTracker.
Running it as part of chrome's browser_tests is a more realistic
simulation of its production behavior. (Plus, we would like to deprecate
extensions_browsertests.)

This CL moves the ContentScriptMatchingBrowserTest to //chrome/browser,
so it's closer to where similar tests are and so that we can take
advantage of ChromeTestExtensionLoader and other chrome/browser-only
fixtures.

Bug: none
Change-Id: I9eceb41844251887e2d013d05e971301f8345e84
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6786411
Commit-Queue: James Cook <jamescook@chromium.org>
Reviewed-by: Zhengzheng Liu <zhzhliu@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1492254}