Rollup merge of #138412 - cuviper:licenses, r=jieyouxu

Install licenses into `share/doc/rust/licenses`

This changes the path from "licences" to "licenses" for consistency
across the repo, including the usage directly around this line. This is
a US/UK spelling difference, but I believe the US spelling is also more
common in open source in general.

Author: matthiaskrgr