bridge: Add ResultTypeInfo for Box<[Vec<u8>]>

Not actually distinct from Vec<Vec<u8>>, but works better with the
jni_result_type and ffi_result_type macros because `[Vec<u8>]` is a
single grouped token tree. Generalizes the string array helpers to
support bytestrings too.

rust/bridge/ffi/src/lib.rs

@@ -50,7 +50,7 @@ pub unsafe extern "C" fn signal_free_lookup_response_entry_list(
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn signal_free_string_array(array: StringArray) {
+pub unsafe extern "C" fn signal_free_bytestring_array(array: BytestringArray) {
     drop(array.into_boxed_parts())
 }