extensions: Add "events" and related tests to desktop Android build

The chrome.events "API" is more like a namespace for events that an
extension can respond to. Fully add its schema to the desktop Android
build (previously we just compiled types for it).

The API implementation is in //extensions/browser/api/declarative/,
which is already compiled on desktop Android. The API impl relies on
a rules registry, which has tests in //chrome/browser/extensions.
Add those unit tests to desktop Android.

I can't port declarative_apitest.cc because it relies on the
declarative web request API, which is deprecated and will not be
ported to desktop Android. However, we should get some coverage for
events as we bring up other API tests.

Bug: 418039049
Change-Id: I1bc6c902824a5828a5c27a4175f9f7c26629729e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6553487
Commit-Queue: James Cook <jamescook@chromium.org>
Reviewed-by: David Bertoni <dbertoni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1461116}