config.py: remove bit array field type's byte order property

config.py: remove bit array field type's byte order property

This patch removes the byte order property from the `_BitArrayFieldType`
class.

Instead, barectf always uses the configuration's target byte order.

As of this version of barectf, where all integral tracing function
parameters are copies, it makes no sense, for example, for a
little-endian CPU to write big-endian data.

The `byte-order` property is also removed in barectf 3 YAML field types.
I'm keeping it in barectf 2 YAML field types for backward compatibility,
but it's ignored now.

From a CTF consumer's perspective, this patch doesn't cause a noticeable
change: the decoded integral value is the same whatever the byte order.

From the barectf API's perspective, it makes the configuration objects
simpler. This patch effectively reverts 7fffc7d ("config: replace trace
type's default BO with configuration's target BO").

It is possible that barectf needs specific bit array field type byte
orders in the future, for example to copy some user payload as is
instead of copying each field; when this time comes, we can reintroduce
the property, adding a way to mark a bit array field type's byte order
as "target" (which would be the default), for example:

    my_ft = barectf.RealFieldType(32,
                                  byte_order=barectf.TARGET_BYTE_ORDER)

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>