feat: As a user, I want kubernetes service discovery to support more configuration items

### Description

Recently, we deployed apisix on different clouds and used the feature of kubernetes service discovery. The problem is that on different clouds, the proxy layer (LB) in front of apiserver has different idle timeouts. However, in apisix's kubernetes service discovery, The time of a watch is fixed, which will cause a problem: when there is no endpoints event in the cluster for a long time, the server will time out instead of the client, and then the service discovery will restart the list-watch after a fixed 40 seconds , so if you can add some configuration items, such as the duration of a watch, retry time or strategy, etc., thank you!

Start by locating APISIX's Kubernetes service discovery list-watch entry point and the current fixed 40-second watch behavior. Review the existing service-discovery tests and configuration conventions before deciding which watch duration, retry timing, or retry strategy is required. Done means the behavior is configurable and remains reliable across clouds with different API-server load-balancer idle timeouts.

Written by the indexing model from the issue text.