feat: ability to set custom team id when creating a team

[yuryfomichov]

Summary

Adds support for optional team_id parameter to the litellm_team resource.

Changes

• Add team_id as optional, computed field with ForceNew=true
• Allow users to specify custom team_id or auto-generate UUID if not provided
• Update documentation with team_id parameter details
• Maintain backward compatibility

Usage

resource "litellm_team" "custom" {
  team_id = "my-custom-id"
  team_alias = "my-team"
}