Drop requirement for __flo_storage in the input binary.

Summary:
We used to require pre-allocated space in the input binary so that
we can write extra sections in there (.eh_frame, .eh_frame_hdr,
.gcc_except_table, etc.). With this diff there's no further
need for pre-allocated storage as we create a new segment and
can use as much space as needed.

There are certain limitations on where the new segment could
be allocated, and as a result the size of the file may increase.

There's currently a limitation if the binary size is close to 4GB
we cannot allocate new segment prior to that and as a result
we require debug info to be stripped to reduce the file size.
The fix is in progress.

(cherry picked from FBD2916029)