BaseTools: Move Build Cache related function out of CreateAsBuiltInf

BaseTools: Move Build Cache related function out of CreateAsBuiltInf

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=1932
There are two functions in current CreateAsBuiltInf, Copy Binary files
to build cache folder and create asbuild inf file.

This patch is to separate UpdateBuildCache and CreateAsBuiltInf into
two functions.

Signed-off-by: Bob Feng <bob.c.feng@intel.com>
Cc: Steven Shi <steven.shi@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Christian Rodriguez <christian.rodriguez@intel.com>
Reviewed-by: Steven Shi <steven.shi@intel.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>