refactor: remove dead API, rename to_disk/config_is_remote_dest, fix perror newlines

- Delete unused public array_list_extend (made static)
- Delete legacy 16-parameter parallel_scanner_create wrapper; migrate test to parallel_scanner_create_with_options
- Rename to_disk -> file_write_to_disk and is_remote_dest -> config_is_remote_dest for module_action naming convention
- Remove stray newlines in perror calls (perror already appends one)

tests/test_property.c

@@ -84,7 +84,7 @@ static void test_property_chunk_roundtrip() {
     for (int i = 0; i < content_len; i++)
       content[i] = (char)(rand() % 256);
 
-    to_disk(path, content, content_len, false, false);
+    file_write_to_disk(path, content, content_len, false, false);
 
     struct stat st;
     stat(path, &st);