plugins ext FEATURE initial schema-mount support

Only for XML data for now. Includes lots of other
changes needed to support this extension.
diff --git a/tests/utests/basic/test_context.c b/tests/utests/basic/test_context.c
index 7899079..8b79a1c 100644
--- a/tests/utests/basic/test_context.c
+++ b/tests/utests/basic/test_context.c
@@ -440,7 +440,10 @@
     struct lys_glob_unres unres = {0};
 
     unsigned int index = 0;
-    const char *names[] = {"ietf-yang-metadata", "yang", "ietf-inet-types", "ietf-yang-types", "ietf-datastores", "ietf-yang-library", "a", "a", "a"};
+    const char *names[] = {
+        "ietf-yang-metadata", "yang", "ietf-inet-types", "ietf-yang-types", "ietf-yang-schema-mount",
+        "ietf-datastores", "ietf-yang-library", "a", "a", "a"
+    };
 
     assert_int_equal(LY_SUCCESS, ly_in_new_memory(str0, &in0));
     assert_int_equal(LY_SUCCESS, ly_in_new_memory(str1, &in1));
@@ -507,7 +510,7 @@
     while ((mod = (struct lys_module *)ly_ctx_get_module_iter(UTEST_LYCTX, &index))) {
         assert_string_equal(names[index - 1], mod->name);
     }
-    assert_int_equal(9, index);
+    assert_int_equal(10, index);
 
     /* cleanup */
     ly_in_free(in0, 0);