路由的占位符解析和查询参数的解析覆盖问题

router.cpp示例中：
https://github.com/ithewei/libhv/blob/0325f2d07f10986139174ff2db75dd151c09b605/examples/httpd/router.cpp#L131-L134

这里路由占位符的解析是在Handler::restful中调用了HttpContext的param，即HttpRequest的GetParam：
https://github.com/ithewei/libhv/blob/0325f2d07f10986139174ff2db75dd151c09b605/examples/httpd/handler.cpp#L171-L179

这个方法是查询参数的解析，这样合在一起会导致这里占位符的解析覆盖了查询参数的解析，如对于/api/test/{str}，会导致 GET http://ip:port/api/test/xxx?str=yyy 后，服务器获取查询参数param("str")时，xxx会覆盖yyy

Start with the route registration in examples/httpd/router.cpp around lines 131-134, then trace Handler::restful and HttpRequest::GetParam in examples/httpd/handler.cpp around lines 171-179. Reproduce the issue with /api/test/xxx?str=yyy and inspect how the path placeholder and query parameter are resolved. Done means the placeholder no longer overrides the query parameter named str.

Scritto dal modello di indicizzazione a partire dal testo della issue.