logger: refactor with configurable implemention

[myfreeer]

Currently we use log4js as the logger, but users may want to use other logging framework or implement logger themselves.

• Loggers are initialized in the init life cycle of the main thread.
• Logger should be returned by a function as implemention of interfaces.
• Messages of the worker threads are sent to the main thread and logged by the worker of main thread.
• Logger initializer should only be invoked in the main thread.
• The dependency of log4js should probably removed with adapters, a default console-based implemention should be provided instead.
• This change should be considered breaking.

export interface Logger {
    trace(type: LogType, ...contents: unknown[]): void;
    debug(type: LogType, ...contents: unknown[]): void;
    info(type: LogType, ...contents: unknown[]): void;
    warn(type: LogType, ...contents: unknown[]): void;
    error(type: LogType, ...contents: unknown[]): void;
}

LogType may include:

• io
  • http
    • request
    • response
    • notFound
    • retry
  • disk
    • mkdir
• system
  • skip
  • skipExternal
  • complete
  • adjustConcurrency
• custom

[myfreeer]

Maybe after #102 we can make most of logging as optional listeners