The encodings are thread-safe and already used in such a manner in other places.
This isn't done where Byte Order Mark output is suppressed, since Encoding.UTF8 is constructed to output the BOM.
The region dearchive module assumes extra null bytes will be appended
to the end of every OAR file. This may be due to the block nature of
storage but it seems like an unsafe assumption. When streaming region
archives over a network or through a memory stream, no additional null
bytes are added to the end and this an exception.
