msi: Implement a second cabinet extractor on top of IStream and use it to extract embedded cabinets.

Currently a cabinet stream is read into memory and then written to a file,
which is then extracted like an external cabinet file. This uses more time
and disk space than necessary and fails if the cabinet is too large to fit
into memory.

msi: Display the file identifier instead of the filename in the SelfRegModules and SelfUnregModules actions.