feat(ci): build cache

[erikburt]

Setup proper module and go build caches for unit/race tests, other small maintenance tasks.

Changes

• Create go-mod-cache.yml workflow, responsible for populating the module cache
• Create setup-go reusable action based off the one in chainlink repo
  • This sets a build cache on pushes to trunk, so subsequent PRs should be able to restore and utilize this cache.

Maintenance changes

• Remove refs to deprecated push-gha-metrics-action
• Pin actions/checkout to v4
• Small formatting changes
• Bump ci-sonarqube-go action

Testing

• go mod cache: https://github.com/smartcontractkit/chainlink-common/actions/runs/16356938577/job/46217401338?pr=1412
  • should normally only run on pushes to main
• go build cache: https://github.com/smartcontractkit/chainlink-common/actions/runs/16357278062/job/46218436100?pr=1412#step:15:6
  • should normally only be created on pushes to main

---

DX-1455