Terraform: Modernize teleport_bot resource

[boxofrad]

This is an alternative to #60310 which is far less disruptive to the user, but much more complex internally.

It evolves the teleport_bot resource such that:

• The top-level name, roles, and traits attributes are now deprecated, and have been replaced with RFD 153-style metadata and spec objects to match our other resources
• We no longer delete and recreate bots during updates (unless the bot name has changed)
• You can now import teleport_bot resources

The complexity stems from the fact that, because the Terraform provider's version is directly coupled to the auth server version, making backward-incompatible changes to resource schema is additionally disruptive. So we want to support both the old and new "schemas" at the same time, and allow the user to update their configuration when they're ready.

An alternative would be to increment the schema "version" and provide a StateUpgrade method, but this would still require the user to update their configuration before the next run.

# Before (this will still work unmodified, with deprecation warnings!)
resource "teleport_bot" "rocket_launcher" {
  name  = "rocket-launcher"
  roles = ["access"]

  traits = {
    logins = ["ubuntu", "root"]
  }
}

# After
resource "teleport_bot" "rocket_launcher" {
  metadata = {
    name  = "rocket-launcher"
  }

  spec = {
    roles = ["access"]

    traits = {
      logins = ["ubuntu", "root"]
    }
  }
}

It is not permissible to mix and match old and new-style attributes, because this makes the mapping to/from protobuf more complex.

# This is not allowed
resource "teleport_bot" "rocket_launcher" {
  name = "rocket-launcher"

  metadata = {
    labels = {
      team = "engineering"
    }
  }

  roles = ["access"]

  spec = {
    traits = {
      logins = ["root"]
    }
  }
}

Closes #40654, #51555, #56910.

changelog: Terraform: teleport_bot resource now supports import, and follows the standard resource structure

[github-actions]

Amplify deployment status

Branch	Commit	Job ID	Status	Preview	Updated (UTC)
boxofrad/evolve-bot-resource	490f750	3	✅SUCCEED	boxofrad-evolve-bot-resource	2025-10-28 12:40:40

[strideynet]

Does this need a label for v18 backport?

[backport-bot-workflows]

@boxofrad See the table below for backport results.

Branch	Result
branch/v18	Create PR