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)

src/client/scanner.h

@@ -77,13 +77,6 @@ Chunk* directory_scanner_next(DirectoryScanner* scanner);
 bool directory_scanner_failed(const DirectoryScanner* scanner);
 void directory_scanner_destroy(DirectoryScanner* scanner);
 
-ParallelScanner* parallel_scanner_create(const char* root_directory, bool use_metadata,
-                                         unsigned long long chunk_size, char** exclude_patterns,
-                                         int exclude_count, char** include_patterns,
-                                         int include_count, unsigned long long max_size,
-                                         unsigned long long min_size, int max_depth,
-                                         int num_threads, bool follow_symlinks, bool copy_links,
-                                         bool safe_links, bool copy_unsafe_links, bool checksum);
 ParallelScanner* parallel_scanner_create_with_options(const char* root_directory,
                                                       const ScannerOptions* options);
 Chunk* parallel_scanner_next(ParallelScanner* scanner);