Ability to send custom fetch options via Watch

[chiragjn]

In the current client that depends on request we can pass an extra requestImpl in Watch which allows us to customize how various requests attributes like keepalive, timeouts, etc

On the new 1.x rc releases we see this option was removed entirely. We were wondering how can we pass on options for applyToFetchOptions via Watch API

Example Code
We are trying to port the the following code on the new node-fetch version

import { KubeConfig, ListPromise, Watch, RequestResult } from '@kubernetes/client-node';
export const webRequest = (opts: OptionsWithUri): RequestResult => { 
    ...
    axios.request({
        ...
        httpsAgent: new Agent({
            ...
            keepAlive: true,
            keepAliveMsecs: 5000,
            timeout: 5000,
          }),
         ...
    })

}
...
const watch = new Watch(kubeConfig, { webRequest });
const informer = new Informer<T>(path, watch, listPromiseFn, enableCache);

Environment (please complete the following information):

• OS: Linux
• NodeJS Version: 20.x
• Cloud runtime N/A

[brendandburns]

I think we could probably add something similar for fetch. We'd be happy to take a PR to add this.