BaseTools: refine CreateAsBuiltInf function

BaseTools: refine CreateAsBuiltInf function

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=1932
ModuleAutogen.CreateAsBuiltInf IsOnlyCopy parameter
and related function can be moved out of CreateAsBuiltInf,
so that CreateAsBuiltInf is more clean.

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