refactor(gitlab): Use new http wrapper for Gitlab platform (#6275)

lib/config/presets/gitlab/index.ts

lib/datasource/gitlab-tags/index.ts

lib/platform/gitlab/gl-got-wrapper.ts

lib/platform/gitlab/index.ts

lib/util/http/__snapshots__/gitlab.spec.ts.snap

lib/util/http/gitlab.spec.ts

lib/util/http/gitlab.ts

lib/workers/pr/changelog/__snapshots__/gitlab.spec.ts.snap

lib/workers/pr/changelog/gitlab.spec.ts

lib/workers/pr/changelog/release-notes.ts

lib/workers/pr/changelog/source-gitlab.ts