Currently we already have a kernel-shared/uuid-tree.c, which is mostly
shared with kernel.
Kernel also has a uuid-tree.h, but we are still using ctree.h for the
header.
Move all the uuid-tree related definitions to kernel-shared/uuid-tree.h,
making future code sync easier.
Signed-off-by: Qu Wenruo <wqu@suse.com>