Add pagination support for gitlab_group_subgroups data source

Bug Report

Only first 20 subgroups are returned in a gitlab_group_subgroups data source.

Relevant Terraform Configuration

data "gitlab_group_subgroups" "subgroups" {
  group_id = "<id>"
}

Relevant Terraform Command

terraform apply

Additional Details

• GitLab Terraform Provider Version: 16.2.0
• GitLab Version: 15.11.0
• Terraform Version: 1.3.6