Fix non-empty plan after mixing CloudSQL with other mounts

[wiktorn]

Closes: #2698
Testcase:

module "project" {
  source         = "./fabric/modules/project"
  name           = var.project_id
  project_create = false
  services = ["file.googleapis.com"]
}

module "bucket" {
  source     = "./fabric/modules/gcs"
  project_id = var.project_id
  prefix     = var.prefix
  name       = "my-bucket"
  location   = var.region
  versioning = true
  labels = {
    cost-center = "devops"
  }
  iam = {
    "roles/storage.objectAdmin" = ["serviceAccount:${module.project.default_service_accounts.compute}"]
  }
}

module "bucket2" {
  source     = "./fabric/modules/gcs"
  project_id = var.project_id
  prefix     = var.prefix
  name       = "my-bucket2"
  location   = var.region
  versioning = true
  labels = {
    cost-center = "devops"
  }
  iam = {
    "roles/storage.objectAdmin" = ["serviceAccount:${module.project.default_service_accounts.compute}"]
  }
}

resource "google_filestore_instance" "instance" {
  project  = var.project_id
  name     = "test-provisioning"
  location = "${var.region}-b"
  tier     = "BASIC_HDD"

  file_shares {
    capacity_gb = 1024
    name        = "share1"
  }

  networks {
    network      = var.vpc.id
    modes        = ["MODE_IPV4"]
    connect_mode = "PRIVATE_SERVICE_ACCESS" # works
  }
}



module "cloudsql-instance" {
  source     = "./fabric/modules/cloudsql-instance"
  project_id = var.project_id
  network_config = {
    connectivity = {
      psc_allowed_consumer_projects = [var.project_id]
    }
  }
  ## define a consumer project with an endpoint within the project
  name                          = "db"
  region                        = var.region
  availability_type             = "REGIONAL"
  database_version              = "POSTGRES_13"
  tier                          = "db-g1-small"
  gcp_deletion_protection       = false
  terraform_deletion_protection = false
}

module "cloud_run" {
  source     = "./fabric/modules/cloud-run-v2"
  project_id = var.project_id
  name       = "hello"
  region     = var.region
  create_job = false
  containers = {
    hello = {
      image = "us-docker.pkg.dev/cloudrun/container/hello"
      env = {
        VAR1 = "VALUE1"
        VAR2 = "VALUE2"
      }
      volume_mounts = {
        acredentials = "/cred1"
        anfs         = "/nfs1"
        bucket       = "/bucket2"
        bempty_dir   = "/empty1"
        cloudsql     = "/cloudsql"
        empty_dir    = "/empty2"
        website      = "/bucket"
        zcredentials = "/cred2"
        znfs         = "/nfs2"
      }
    }
  }
  revision = {
    gen2_execution_environment = true
        vpc_access = {
      egress = "ALL_TRAFFIC"
      subnet = var.subnet.name
    }
  }
  volumes = {
    website = {
      gcs = {
        bucket       = module.bucket2.name
        is_read_only = false
      }
    }
    cloudsql = {
      cloud_sql_instances = [module.cloudsql-instance.connection_name]
    }
    bucket = {
      gcs = {
        bucket       = module.bucket.name
        is_read_only = false
      }
    }
    bempty_dir = {
      empty_dir_size = 1
    }
    empty_dir = {
      empty_dir_size = 1
    }
    acredentials = {
      secret = {
        name    = module.secret-manager.secrets["credentials"].id
        path    = "my-secret"
        version = "latest" # TODO: should be optional, but results in API error
      }
    }
    zcredentials = {
      secret = {
        name    = module.secret-manager.secrets["credentials"].id
        path    = "my-secret"
        version = "latest" # TODO: should be optional, but results in API error
      }
    }
    anfs = {
      nfs = {
        server = google_filestore_instance.instance.networks[0].ip_addresses[0]
        path   = "/share1"
      }
    }
    znfs = {
      nfs = {
        server = google_filestore_instance.instance.networks[0].ip_addresses[0]
        path   = "/share1"
      }
    }
  }
  deletion_protection = false
}

---

Checklist

I applicable, I acknowledge that I have:

• Read the contributing guide
• Ran terraform fmt on all modified files
• Regenerated the relevant README.md files using tools/tfdoc.py
• Made sure all relevant tests pass