Use lib instead of libs for require path

[trans]

It would be better to use lib (singular) rather than libs (plural) for a few reasons.

1. The Unix standard name for such directory is lib. Probably every developer knows this.
2. The plural is superfluous, it doesn't really provide any addition semantic information.
3. Plurals tend to be used inconsistently in projects, e.g. doc or docs, tests or test.

For these reasons it would be better to stick with more abbreviated singular lib.

[miketheman]

#triage
This issue has moved from draft to accepted recently. The implementation appears to be underway in related issues.

[asterite]

Yes, this depends on #2788, which in turns depends on shards adopting this new logic