feat: initial admin PAT has IAM_LOGIN_CLIENT (#10143)

# Which Problems Are Solved

We provide a seamless way to initialize Zitadel and the login together.

# How the Problems Are Solved

Additionally to the `IAM_OWNER` role, a set up admin user also gets the
`IAM_LOGIN_CLIENT` role if it is a machine user with a PAT.

# Additional Changes

- Simplifies the load balancing example, as the intermediate
configuration step is not needed anymore.

# Additional Context

- Depends on #10116 
- Contributes to https://github.com/zitadel/zitadel-charts/issues/332
- Contributes to https://github.com/zitadel/zitadel/issues/10016

---------

Co-authored-by: Stefan Benz <46600784+stebenz@users.noreply.github.com>

internal/domain/roles.go

@@ -14,6 +14,7 @@ const (
 	RoleOrgOwner             = "ORG_OWNER"
 	RoleOrgProjectCreator    = "ORG_PROJECT_CREATOR"
 	RoleIAMOwner             = "IAM_OWNER"
+	RoleIAMLoginClient       = "IAM_LOGIN_CLIENT"
 	RoleProjectOwner         = "PROJECT_OWNER"
 	RoleProjectOwnerGlobal   = "PROJECT_OWNER_GLOBAL"
 	RoleProjectGrantOwner    = "PROJECT_GRANT_OWNER"