zfs: replace uu_avl with sys/avl

Lets just use the AVL implementation we use everywhere else.

Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17934

lib/libuutil/Makefile.am

@@ -5,14 +5,12 @@ CPPCHECKTARGETS += libuutil.la
 
 libuutil_la_SOURCES = \
 	%D%/uu_alloc.c \
-	%D%/uu_avl.c \
 	%D%/uu_ident.c \
 	%D%/uu_list.c \
 	%D%/uu_misc.c \
 	%D%/uu_string.c
 
 libuutil_la_LIBADD = \
-	libavl.la \
 	libspl.la
 
 libuutil_la_LIBADD += $(LTLIBINTL)