chore: add a config check (#14327)

Add a presubmit check to verify library name and version are consistent
among `state.yaml` and `librarian.yaml`.

Update the version of pubsub and pubsub/v2 since these two libraries are
released with an old version of legacylibrarian. Using legacylibrarian
v0.9.1 and above will update version in librarian.yaml automatically.

For googleapis/librarian#4422

Author: JoeWang1127

.github/workflows/config_check.yml

@@ -0,0 +1,40 @@
+---
+name: config check
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+permissions:
+  contents: read
+jobs:
+  config-check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      # Use this action, rather than a file filter so that we can make this
+      # mandatory.
+      # See https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-syntax#example-including-branches
+      # for more details.
+      - uses: dorny/paths-filter@v4
+        id: filter
+        with:
+          filters: |
+            librarian:
+              - 'librarian.yaml'
+              - '.librarian/**'
+      - name: Config check
+        if: steps.filter.outputs.librarian == 'true'
+        run: |
+          V="$(sed -n 's/^version: *//p' librarian.yaml)"
+          go run "github.com/googleapis/librarian/tool/cmd/configcheck@${V}" .
+      - name: Update library versions and regenerate
+        if: failure()
+        run: |
+          echo "Library version is different between state.yaml and librarian.yaml.
+          Update versions in the configs according to the error message and
+          regenerate libraries using:
+          
+          V=\$(sed -n 's/^version: *//p' librarian.yaml)
+          go run github.com/googleapis/librarian/cmd/librarian@\${V} generate --all
+          "

internal/generated/snippets/pubsub/v2/apiv1/snippet_metadata.google.pubsub.v1.json

@@ -8,7 +8,7 @@
     ],
     "language": "GO",
     "name": "cloud.google.com/go/pubsub/v2/apiv1",
-    "version": "2.5.0"
+    "version": "2.5.1"
   },
   "snippets": [
     {

librarian.yaml

@@ -939,15 +939,15 @@ libraries:
       - README.md
       - internal/version.go
   - name: pubsub
-    version: 1.50.1
+    version: 1.50.2
     keep:
       - README.md
       - internal/version.go
     skip_release: true
     go:
       nested_module: v2
   - name: pubsub/v2
-    version: 2.5.0
+    version: 2.5.1
     apis:
       - path: google/pubsub/v1
     keep: