schema CHANGE rename lys_atomize_xpath() and the connected options

Unify name of lys_atomize_xpath() with the connected lys_find_xpath().
The function is now named lys_find_xpath_atoms() and the options used in
both functions are LYS_FIND_XP* (thei internally maps to a bigger group
of options LYXP_*).

Unifying all the names should make API usage more easier.
diff --git a/src/tree_schema.c b/src/tree_schema.c
index f1a170f..2ecace5 100644
--- a/src/tree_schema.c
+++ b/src/tree_schema.c
@@ -228,7 +228,7 @@
 }
 
 API LY_ERR
-lys_atomize_xpath(const struct lysc_node *ctx_node, const char *xpath, uint32_t options, struct ly_set **set)
+lys_find_xpath_atoms(const struct lysc_node *ctx_node, const char *xpath, uint32_t options, struct ly_set **set)
 {
     LY_ERR ret = LY_SUCCESS;
     struct lyxp_set xp_set;