Add user and group management capability to coderd provider

[johnstcn]

Should cover use cases similar to the following:

// Create a bot user for Jenkins
resource "coderd_user" "jenkins" {
  username = "jenkins"
  name     = "Jenkins CI/CD"
  email    = "ci@example.com"
  roles    = ["template-admin"]
  login_type = "none"
}

// Keep the password of a user account up to date from an external source
resource "coderd_user" "audit" {
  username = "auditor"
  name     = "Auditor"
  email    = "security@example.com"
  roles    = ["auditor"]
  login_type = "password"
  password = data.vault_password.auditor.value
}

// Ensure the admin account is suspended
resource "coderd_user" "admin" {
  username = "admin"
  suspended = true
}

// Only the following can admin
resource "coderd_group" "bosses" {
  display_name = "The Bosses"
  members = [
    data.coder_user.jon.id
    data.coder_user.ammar.id
    data.coder_user.kyle.id
    data.coder_user.rob.id
  ]
}

[ethanndickson]

Closed by #18, #19, #31, #32