(PUP-839) FFI Security.set_security_descriptor

• Previously SetSecurityDescriptor was using a reference to the API definition in windows/security, but has now been replaced with FFI.
• Define the SE_OBJECT_TYPE enum to be passed to SetSecurityInfo
• Rather than hardcoding the buffer size for the DACL to 1024, provide a calculation to determine the maximum size up-front based on the number of ACEs in the security descriptor. This will at least guarantee that the memory buffer is never too small, which could have been an issue with the existing code. Note that a more correct method would be to translate each SID in the DACL up-front to a sid_ptr, and to tally up the size of the SIDs.
• Since only ACCESS_DENIED_ACE and ACCESS_ALLOWED_ACE are added to the DACL, use that struct size in the calculation by referring to number of bytes leading up to the :SidStart member of the GENERIC_ACCESS_ACE struct.