Bidi-wrap the results of format[Short]FileSize().

Previously, users of the results of formatFileSize() and
formatShortFileSize() needed to unicodeWrap the results themselves
using BidiFormatter, which resulted in several bugs and
inconsistencies across the platform when they didn't, especially in
Hebrew and Urdu locales:

Hebrew and Urdu use Latin abbreviations like 'MB' for file sizes
which cause undesired reorderings (or incorrect detection of the
string direction when the formatted file size starts the string).

With this patch, the results are now bidi-wrapped before being
returned if the locale of the context passed in to the formatter is a
right-to-left locale.

Bug: 22237132
Bug: 22273176
Change-Id: If076636d15828fc810feef6f0fa8806ef52aed5d