WhiteBoxTests.cpp is by far the slowest TU
to compile (taking minutes) and gcc started showing
'note: variable tracking size limit exceeded'
and recompiles, which doubles the time.
This moves the StringVector tests into a new
home, which reduces the size of WhiteBoxTests.
Change-Id: Ia4e8daa921fb941815ad7e68f4dbb964fb2cd93e
Signed-off-by: Ashod Nakashian <ashod.nakashian@collabora.co.uk>
