Scoped config in waypoint.hcl

[mitchellh]

This introduces the ability to scope configuration in waypoint.hcl to workspaces, labels, and runners. This is the frontend-implementation of the already-merged backend functionality in #2186.

The following shows a single waypoint.hcl example that is using all the functionality introduced in this PR. This is unlikely to be practical, I expect people will use bits and pieces at a time.

project = "foo"

config {
  env = { "ENV" = "default" }

  workspace "dev" {
    env = { "ENV" = "dev" }
  }

  // Could've just used "workspace" here but showing off...
  label "waypoint/workspace is 'production'" {
    env = { "ENV" = "prod" }
  }

  // These apply to on-demand runners only when working on things related
  // to this project.
  runner {
    env = { "BUILD_ENV" = "dev" }
  }
}

app "api" {
  // can use config in here too
}

[evanphx]

Look at all this topological soooorting! /cc @izaaklauer