Why SentinelGatewayFilter implements GatewayFilter and GlobalFilter together?

是不是只要实现一个 GlobalFilter 就行了, 实现 GatewayFilter 的意义在哪?

Start by reading the SentinelGatewayFilter implementation and the GatewayFilter and GlobalFilter entry points referenced by the issue title. Trace how the filter is registered and invoked, then determine whether both interfaces are required or whether one can be removed. Done means providing a clear rationale, with any affected behavior or documentation identified.

Written by the indexing model from the issue text.