ci: add Dependabot recursive go mod tidy support (gnolang#1412)

## Description

This PR introduces a simple workflow that tidies go mod files on
Dependabot PRs, and turns off the mod check for those PRs (to avoid
overlapping workflows).

<details><summary>Contributors' checklist...</summary>

- [x] Added new tests, or not needed, or not feasible
- [x] Provided an example (e.g. screenshot) to aid review or the PR is
self-explanatory
- [x] Updated the official documentation or not needed
- [x] No breaking changes were made, or a `BREAKING CHANGE: xxx` message
was included in the description
- [ ] Added references to related issues and PRs
- [ ] Provided any useful hints for running manual tests
- [ ] Added new benchmarks to [generated
graphs](https://gnoland.github.io/benchmarks), if any. More info
[here](https://github.com/gnolang/gno/blob/master/.benchmarks/README.md).
</details>

---------

Co-authored-by: Guilhem Fanton <[email protected]>
Co-authored-by: Manfred Touron <[email protected]>

.github/workflows/dependabot-tidy.yml

@@ -0,0 +1,41 @@
+name: Dependabot Tidy Go Mods
+
+on:
+  pull_request:
+    paths:
+      - '.github/workflows/**'
+      - '**/go.mod'
+      - '**/go.sum'
+
+jobs:
+  tidy_go_mods:
+    runs-on: ubuntu-latest
+    if: ${{ github.actor == 'dependabot[bot]' }}
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Install Go
+        uses: actions/setup-go@v4
+        with:
+          go-version: 1.21.x
+
+      - name: Tidy all Go mods
+        run: |
+          set -e
+          # Find all go.mod files
+          gomods=$(find . -type f -name go.mod)
+          
+          # Tidy each go.mod file
+          for modfile in $gomods; do
+            dir=$(dirname "$modfile")
+          
+            # Run go mod tidy in the directory
+            (cd "$dir" && go mod tidy -v) || exit 1
+          done
+
+      - name: Commit changes, if any
+        uses: stefanzweifel/git-auto-commit-action@v5
+        with:
+          skip_dirty_check: false # Enable dirty check, and skip unnecessary committing
+          commit_message: "Run 'go mod tidy' via GitHub Actions"

.github/workflows/lint.yml

@@ -58,8 +58,9 @@ jobs:
           else
             echo 'Succeeded.'
           fi
-  modtidy:
+  mod_tidy_check:
     runs-on: ubuntu-latest
+    if: ${{ github.actor != 'dependabot[bot]' }}
     steps:
       - name: Checkout code
         uses: actions/checkout@v4