feat(go): Support GOPROXY (#9150)

docs/usage/configuration-options.md

lib/datasource/go/__fixtures__/go-kit.list.txt

lib/datasource/go/__snapshots__/goproxy.spec.ts.snap

lib/datasource/go/__snapshots__/index.spec.ts.snap

lib/datasource/go/common.ts

lib/datasource/go/goproxy.spec.ts

lib/datasource/go/goproxy.ts

lib/datasource/go/index.spec.ts

lib/datasource/go/index.ts

lib/datasource/go/types.ts