Fix: Field types native byte order refers to the trace

Fix: Field types native byte order refers to the trace

Following a misunderstanding of the CTF specification, the native
byte order was implemented as meaning the host's endianness. It should
refer to the Trace's endianness.

This modification ensures that stream classes, event classes and field
types correctly inherit the trace's endianness when "native" is used.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>