feat(gitlab-release): implement datasource (#11226)

lib/datasource/api.ts

...tasource/gitlab-releases/__snapshots__/index.spec.ts.snap

lib/datasource/gitlab-releases/index.spec.ts

lib/datasource/gitlab-releases/index.ts

lib/datasource/gitlab-releases/types.ts

lib/datasource/gitlab-tags/index.ts

lib/types/platform/gitlab/index.spec.ts

lib/types/platform/gitlab/index.ts

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

lib/util/http/auth.ts

lib/util/http/gitlab.spec.ts

lib/util/http/gitlab.ts