terraform-provider-random2: Import terraform-provider-random2 as net/terraform-provider-random2

Replace net/terraform-provider-random by adding a suffix version
so multiple random providers can coexists.

Adapt to terraform/provider.mk so that the provider can be used with
Terraform and OpenTofu.
Please note that now it no longer depends on terraform or opentofu so
the desired version should be manually installed.

Also migrate it to lang/go/go-module.mk.
