Break out the range_tree, btree, and highbit64/lowbit64 code from kernel
space into shared kernel and userspace code. This is needed for the
updated `zpool status -vv` error byte range reporting that will be
coming in a future commit. That commit needs the range_tree code in
kernel and userspace.
Reviewed-by: Rob Norris <robn@despairlabs.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tony Hutter <hutter2@llnl.gov>
Closes#18133
