tools: First pass at a pipeline config

This is used by Librarian to provide environment variables to
container commands. The values can be provided either by environment
variables in the host, or by Secret Manager.

Author: jskeet

generator-input/pipeline-config.json

@@ -0,0 +1,16 @@
+{
+  "commands": {
+    "integration-test-library": {
+      "environmentVariables": [
+        {
+          "name": "TEST_PROJECT",
+          "secretName": "integration-test-project"
+        },
+        {
+          "name": "FIRESTORE_TEST_PROJECT",
+          "secretName": "firestore-test-project"
+        }
+      ]
+    }
+  }
+}