Discover Wizard: allow label filters when creating auto-enrollment configurations

[marcoandredinis]

What would you like Teleport to do?
When enrolling a new resource in Teleport Web UI, for AWS resources we can set the region (and VPC for RDS DBs) that we want to auto discover.

This might be too generic for some users, and bring resources that the user doesn't want to be controlled by Teleport.

Users should be able to set label matchers as filters for the resources they would like to access from Teleport.

What problem does this solve?

Being able to enroll only a subset of resources instead of everything from a region.

If a workaround exists, please include it.
For users to do this, they need to change the discovery_config resource created during the flow.
tctl get discovery_config gets all the discovery configs.
Locate the one you want to change.
tctl edit discovery_config/<name> and add the labels like so

  aws:
   - types: ["ec2"]
     regions: ["us-east-1"]
     tags:
       env: stg