Reland "Don't use framework strings for formatting file sizes"

Reland http://ag/2529020 because the over-translation issue should be
resolved now.

Modify various formatters to avoid using framework strings for
formatting file sizes.

Also update README instructions for running unit tests.

Bug: 36994779
Bug: 71580745
Bug: 217592956
Test: no new test failures from RunSettingsRoboTests
Test: manual opening the settings page.
Change-Id: Ic4689ab1b76622028004d05e69858228bdc441cf