The contents of `includes/services/` (`ServiceContainer` and friends) do not use any MediaWiki-specific code, as far as I can tell, except for the `Assert` library. As such, they could be moved to the `includes/libs/` directory, to signal this fact more clearly, or even extracted into a separate library published to Packagist.
MediaWiki:
- [x] [core: move and rename](https://gerrit.wikimedia.org/r/478729)
- [ ] extensions: update for rename
- [x] [Wikibase](https://gerrit.wikimedia.org/r/479747)
- [x] [WikibaseLexeme](https://gerrit.wikimedia.org/r/479748)
- [x] [BlueSpiceFoundation](https://gerrit.wikimedia.org/r/479749)
- [ ] [Semantic MediaWiki](https://github.com/SemanticMediaWiki/SemanticMediaWiki/issues/3554)
- [x] remove compatibility aliases
Library:
* [x] Create repo.
* [x] Verify GitHub mirror.
* [x] Set up WMF CI.
* [x] Set up Packagist hook.
* [x] Set up code coverage pipeline.
* [x] Set up doxygen pipeline.
* [ ] Add lib to doc.wikimedia.org.