feat: Fleet Resources (BPOP-5000)

[schmikei]

Description of Changes

This PR introduces support for managing fleets via the terraform provider. This includes basic CRUD and follows a lot of our existing resource management lifecycles.

Example usage with a configuration named configuration

resource "bindplane_fleet" "production" {
  name        = "production-fleet"
  description = "Fleet for production agents"
  configuration = bindplane_configuration.configuration.name

  labels = {
    environment = "production"
    team        = "platform"
  }

  selector {
    match_labels = {
      fleet = "production-fleet"
      env   = "prod"
    }
  }

with v2

resource "bindplane_fleet" "staging" {
  name          = "staging-fleet-2"
  description   = "Fleet for staging agents"
  configuration = bindplane_configuration_v2.configuration.name

  labels = {
    environment = "staging"
    team        = "platform"
  }

  selector {
    match_labels = {
      fleet = "staging-fleet"
      env   = "staging"
    }
  }
}

Feel free to create a couple configurations but have tested it working with both v1 and v2 configurations.

Please check that the PR fulfills these requirements

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• CI passes

[jsirianni]

Does the UI wizard ask for these during creation? If so, I think they should be required and force new, at least for now.