BaseTools:Add the spare space FV image size checker

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=2654



If FV is placed in FD region, its FV image size is fixed.
When FV image size exceeds it, it will trig the build break.
To alert the developer to adjust FV image size earlier,
I request to add new checker for the the spare FV space.
When the spare FV space is less than the specified threshold,
build tool will report the error.

This checker is the optional.
It can be enabled by -D FV_SPARE_SPACE_THRESHOLD=10000.
Macro is the value of the spare space threshold size.
It can be decimal or hex format. If it is enabled,
BaseTools will check every FV with the fixed size.
If FV doesn't meet with the size requirement,
Build tool will report error message to say there is no
enough spare space.

Cc: Liming Gao <liming.gao@intel.com>
Cc: Bob Feng <bob.c.feng@intel.com>
Signed-off-by: Zhiju.Fan <zhijux.fan@intel.com>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>