[zeromicro/go-zero]支持内置中间件的自定义（移除内置中间件）

内置的中间件无法删除（中间件只能添加不能删）

func (s *engine) bindRoute(fr featuredRoutes, router httpx.Router, metrics *stat.Metrics,
route Route, verifier func(chain alice.Chain) alice.Chain) error {
chain := alice.New(
    handler.TracingHandler,
    s.getLogHandler(),
    handler.MaxConns(s.conf.MaxConns),
    handler.BreakerHandler(route.Method, route.Path, metrics),
    handler.SheddingHandler(s.getShedder(fr.priority), metrics),
    handler.TimeoutHandler(time.Duration(s.conf.Timeout)*time.Millisecond),
    handler.RecoverHandler,
    handler.MetricHandler(metrics),
    handler.PromethousHandler(route.Path),
    handler.MaxBytesHandler(s.conf.MaxBytes),
    handler.GunzipHandler,
)
chain = s.appendAuthHandler(fr, chain, verifier)

for _, middleware := range s.middlewares {
    chain = chain.Append(convertMiddleware(middleware))
}
handle := chain.ThenFunc(route.Handler)

return router.Handle(route.Method, route.Path, handle)
}

某些场景下需要能够删除一些内置的中间件。举个例子：在内置的DetailedLogHandler或者LogHandler中间件无法满足业务需求的情况下，我会自己实现一个LogHandler并注入到go-zero框架，那么在功能上就会和内置的LogHandler重叠并且存在不必要的性能损耗。