Factory based FAST Networking stage (#3435)

New factory based networking stage, shipping with a single dataset (peering) to keep the PR size somewhat manageable.

tests/fast/stages/s2_networking/peerings.tfvars

@@ -0,0 +1,38 @@
+automation = {
+  outputs_bucket = "test"
+}
+billing_account = {
+  id = "000000-111111-222222"
+}
+factories_config = {
+  defaults              = "datasets/hub-and-spokes-peerings/defaults.yaml"
+  dns                   = "datasets/hub-and-spokes-peerings/dns/zones"
+  dns-response-policies = "datasets/hub-and-spokes-peerings/dns/response-policies"
+  firewall-policies     = "datasets/hub-and-spokes-peerings/firewall-policies"
+  folders               = "datasets/hub-and-spokes-peerings/folders"
+  interconnect          = "datasets/hub-and-spokes-peerings/interconnect"
+  ncc-hubs              = "datasets/hub-and-spokes-peerings/ncc-hubs"
+  nvas                  = "datasets/hub-and-spokes-peerings/nvas"
+  projects              = "datasets/hub-and-spokes-peerings/projects"
+  vpcs                  = "datasets/hub-and-spokes-peerings/vpcs"
+}
+
+folder_ids = {
+  "networking"      = "folders/12345678"
+  "networking/prod" = "folders/23456789"
+  "networking/dev"  = "folders/34567890"
+}
+organization = {
+  domain      = "fast.example.com"
+  id          = 123456789012
+  customer_id = "C00000000"
+}
+prefix = "fast"
+service_accounts = {
+  "iac-0/iac-pf-rw" = "iac-pf-rw@test.iam.gserviceaccount.com"
+  "iac-0/iac-pf-ro" = "iac-pf-ro@test.iam.gserviceaccount.com"
+}
+tag_values = {
+  "environment/development" = "tagValues/12345"
+  "environment/production"  = "tagValues/12346"
+}

tests/fast/stages/s2_networking/tftest.yaml

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+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+module: fast/stages/2-networking
+
+tests:
+  peerings: