Any app that targets S+ will need to have an explicit android:exported
defined if intent filters are present for an activity/service/receiver.
Apps failing this requirement will fail to install.

While ANGLE doesn't explicitly target S, to prevent hitting this in the
future we should add android:exported to its AndroidManifest.xml since
we use several receiver intent-filters.

Bug: b/158221251
Test: CQ
Change-Id: I565c6ff5aaf25380d7e6ad2418612ab10f4c185f
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2231249Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Tim Van Patten <timvp@google.com>