lib: adjust son dev/non-dev precondition assertions in field-class.c

lib: adjust son dev/non-dev precondition assertions in field-class.c

I found some functions using BT_ASSERT_PRE_DEV_FC_NON_NULL followed by
either BT_ASSERT_PRE_FC_HAS_TYPE or BT_ASSERT_PRE_FC_IS_STRUCT (i.e. a
dev followed by a non-dev).  This seems illogical to me.  Either the
function is considered "fast path" and we use the dev versions, either
it's not "fast path" and we use the non-dev versions.

Change a few assertions to be dev.  If some of these functions aren't
actually considered fast path, then I think we should switch the
BT_ASSERT_PRE_DEV_FC_NON_NULLs to be non-dev.

Change-Id: I4f0c1cb0ef1006beddcc688d4e71f37fdb561e15
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/7326
Tested-by: jenkins <jenkins@lttng.org>
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/10807
CI-Build: Philippe Proulx <eeppeliteloop@gmail.com>