L7 Routing empty state

## Overview of issue

- If a user hasn't configured any L7 traffic management stages (routers, splitters, resolvers), show an informational banner at the top explaining why the router and resolver is present by default
- Add tooltips to the default router and resolver cards which appear on mouseover

## Desired styling:

### Without TCP protocol

**NOTE:** the images below should have the "Read the documentation" and "Follow the guide" links at the bottom, just like in the "With TCP protocol" image below.

### With TCP protocol

### Links to include in the informational banner
- Read the documentation:
- Icon: use same icon as is [used on the intention page empty state](https://github.com/hashicorp/consul/blob/2d05164be1d30fc6ec2ad0126294e009001e400b/ui/packages/consul-ui/app/templates/dc/intentions/index.hbs#L126-L128)
- Link: https://www.consul.io/docs/connect/l7-traffic
- Follow the guide:
- Icon: use same icon as is [used on the intention page empty state](https://github.com/hashicorp/consul/blob/2d05164be1d30fc6ec2ad0126294e009001e400b/ui/packages/consul-ui/app/templates/dc/intentions/index.hbs#L129-L131)
- Link: https://learn.hashicorp.com/tutorials/consul/service-mesh-traffic-management