Remove StorageMonitor dependency on BrowserProcess

This is first step of making StorageMonitor a component. Previously, the
StorageMonitor was handing over the ownership of the StorageMonitor singleton
to the BrowserProcess object. Now the singleton lives in a StorageMonitor global
but has methods for controlling it's lifecycle externally.

R=joi@chromium.org,thestig@chromium.org
BUG=
Make storage_monitor a component

Move storage_monitor to the components directory and:

- Make the unit tests part of the components unit tests.
- Update the include headers for both chrome and storage_monitor code.
- Update the buildsystem dependencies and paths.
- Update the DEPS files for both chrome and storage_monitor with the new
restrictions.

R=joi@chromium.org,thestig@chromium.org
BUG=
Fix the include guards
Update the buildsystem
Update the include headers for chrome
Update the include headers for storage_monitor
Update the DEPS files