Use JoinScript for DiscoveryService for self-hosted Discovery wizard

[marcoandredinis]

What would you like Teleport to do?
When going through a flow of the Discover wizard that requires a DiscoveryService, teleport should offer an easy way for users to deploy a DiscoveryService.
Instead, we are showing how to run a DiscoveryService:

What problem does this solve?
This instructions, when compared to the rest of the flow, are relatively hard to follow for someone that hasn't used teleport before.

If a workaround exists, please include it.

We already have a JoinScript specifically for DiscoveryService
#36286

An alternative to this would be running a DiscoveryService in Amazon ECS