Rewrite routes to /.auth** should forward to auth server

Before filing this issue, please ensure you're using the latest CLI by running `swa --version` and comparing to the latest version on [npm](https://www.npmjs.com/package/@azure/static-web-apps-cli).

**Are you accessing the CLI from the default port `:4280` ?**

- [ ] No, I am using a different port number (`--port`) and accessing the CLI from that port
- [ X] Yes, I am accessing the CLI from port `:4280`

> Make sure you are accessing the URL printed in the console when running `swa start`!

**ℹ️ NOTE: Make sure to enable debug logs when running any `swa` commands using `--verbose=silly`**

**Describe the bug**
When adding a route rule to rewrite a route to an auth URL (/.auth**), request instead points to the static web server

```
{
"route": "/api/auth",
"rewrite": "/.auth/me"
}
```

Log:

> remote dev server detected.
> - url: /.auth/me
> - target: http://localhost:8080
> customUrl: false
> is4xx: false
> remote dev server detected. Proxying request
> - url: /.auth/me
> - code: 200
> GET http://localhost:8080/.auth/me (proxy)
> Connected to tcp:127.0.0.1:8080 successfully
> http://localhost:8080 validated successfully
> Connected to tcp:localhost:8080 successfully
> getting response from dev server
> GET http://localhost:4280/.auth/me - 404

**To Reproduce**
Add a route rule that redirects to an auth path.

**Expected behavior**
Requests for rewritten routes to /.auth** should be forwarded to the auth server, not static server

Reproduce the route rewrite with `swa start` on port :4280 and enable `--verbose=silly` to inspect how `/.auth/me` is routed. Trace the proxy handling for rewritten `/.auth**` paths; done when those requests reach the auth server instead of the static server.

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