feat(config): Support presets in subdirectories (#8724)

docs/usage/config-presets.md

lib/config/presets/__snapshots__/index.spec.ts.snap

...presets/bitbucket-server/__snapshots__/index.spec.ts.snap

lib/config/presets/bitbucket-server/index.spec.ts

lib/config/presets/bitbucket-server/index.ts

lib/config/presets/gitea/__snapshots__/index.spec.ts.snap

lib/config/presets/gitea/index.spec.ts

lib/config/presets/gitea/index.ts

lib/config/presets/github/__snapshots__/index.spec.ts.snap

lib/config/presets/github/index.spec.ts

lib/config/presets/github/index.ts

lib/config/presets/gitlab/__snapshots__/index.spec.ts.snap

lib/config/presets/gitlab/index.spec.ts

lib/config/presets/gitlab/index.ts

lib/config/presets/index.spec.ts

lib/config/presets/index.ts

lib/config/presets/local/__snapshots__/index.spec.ts.snap

lib/config/presets/local/index.ts

lib/config/presets/types.ts

lib/config/presets/util.ts