(PUP-839) FFI Util::Windows::Security::parse_dacl

• Previously parse_dacl did some byte manipulation that would have likely caused errors in x64. It also used a GetAce API definition that was not FFI'd and therefore would have had incorrect pointer lengths on x64. parse_dacl now accepts an FFI::Pointer as a param rather than an address.
• New FFI structs have been created for ACE, ACE_HEADER and ACL that make casting memory addresses much simpler to reason about.
• An extraneous call to IsValidSid was removed and the code flow was refactored to return sooner in unsupported / failure cases.