add more custom loggers, support user-defined logger callback

[rainyl]

fix: #173

Recently, opencv 4.12.0 adds replaceWriteLogMessage abd replaceWriteLogMessageEx in opencv/opencv#27154

Which makes logging to a file possible, now we support user-defined logger

import 'dart:io';
import 'dart:isolate';

import 'package:dartcv4/dartcv.dart' as cv;
import 'package:logging/logging.dart';

void main(List<String> args) async {
  final logFile = File("log.txt");
  final logger = Logger("")
    ..level = Level.ALL
    ..onRecord.listen((record) {
      logFile.writeAsStringSync("${record.message}\n", mode: FileMode.append);
    });

  cv.setLogLevel(cv.LogLevel.DEBUG);
  cv.replaceWriteLogMessage(
    callback: (level, message) {
      logger.warning(message);
    },
  );

  await Isolate.run<void>(
    () {
      for (var i = 0; i < 100; i++) {
        cv.writeLogMessage(cv.LogLevel.ERROR, "$i hello world");
      }
    },
  );

  print("isolate done");

  cv.replaceWriteLogMessage(callback: null);
}

Currently, this is only supported in 2.x branch, will support 1.x in the future if I have some time.