Require bacdef.h as first bacnet header to include (#598) (#600)

* Require bacdeps.h as first bacnet header to include

BACnet headers need to pull in optional configuration and
optional ecosystem overrides to allow integrators to control
builds.  This commit changes bacnet header files to first
include bacnet/bacdep.h to consistently introduce integrator
header files.

Verified by:

1. make clean all test

2. ./zephyr/scripts/twister -p unit_testing \
        -T bacnet-stack/zephyr/tests/



* Migrate BACNET_UNSIGNED_INTEGER defn to bacdef.h

Verified by:

1. make clean all test

2. ./zephyr/scripts/twister -p unit_testing \
        -T bacnet-stack/zephyr/tests/



---------

Signed-off-by: Gregory Shue <gregory.shue@legrand.com>
Co-authored-by: Greg Shue <32416235+gregshue@users.noreply.github.com>
Co-authored-by: Gregory Shue <gregory.shue@legrand.com>

src/bacnet/basic/object/iv.h

@@ -35,8 +35,8 @@
 
 #include <stdbool.h>
 #include <stdint.h>
+#include "bacnet/bacdef.h"  /* Must be before all other bacnet *.h files */
 #include "bacnet/bacnet_stack_exports.h"
-#include "bacnet/bacdef.h"
 #include "bacnet/bacerror.h"
 #include "bacnet/wp.h"
 #include "bacnet/rp.h"