ci: migrate runs-on to Twilio runner labels + SHA-pin actions

- Target ubuntu-latest-large for the Test matrix and golangci-lint,
  per guidance from Charlotte St. John (segmentio/stats is public, so
  the Twilio self-hosted pool doesn't apply - see PEA-901).
- SHA-pin actions/checkout (v7.0.1) and actions/setup-go (v7.0.0).
- Run golangci-lint (bumped to v2.12.2) via `go install` + a plain
  run: step instead of the golangci/golangci-lint-action marketplace
  action, since that action isn't on this repo's Actions allowlist
  (only github-owned actions are permitted) and was startup-failing
  regardless of runs-on.

Author: kevinburkesegment

.github/workflows/go.yml

@@ -12,15 +12,15 @@ jobs:
           - 'oldstable'
           - 'stable'
         label:
-          - ubuntu-latest
+          - ubuntu-latest-large
 
     runs-on: ${{ matrix.label }}
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
 
       - name: Setup Go (${{ matrix.go }})
-        uses: actions/setup-go@v5
+        uses: actions/setup-go@b7ad1dad31e06c5925ef5d2fc7ad053ef454303e  # v7.0.0
         with:
           go-version: ${{ matrix.go }}
 

.github/workflows/golangci-lint.yml

@@ -16,15 +16,19 @@ name: golangci-lint
 jobs:
   lint:
     name: lint
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-latest-large
     steps:
-      - uses: actions/setup-go@v5
+      - uses: actions/setup-go@b7ad1dad31e06c5925ef5d2fc7ad053ef454303e  # v7.0.0
         with:
           go-version: '>=1.24'
 
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
+
+      - name: Install golangci-lint
+        # https://github.com/golangci/golangci-lint/tags
+        run: |
+          go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@v2.12.2
+          echo "$(go env GOPATH)/bin" >> "$GITHUB_PATH"
 
       - name: golangci-lint
-        uses: golangci/golangci-lint-action@v8
-        with:
-          version: v2.1.6
+        run: golangci-lint run