Rollup merge of #130110 - onur-ozkan:configurable-dist-vendor, r=Kobzol,Mark-Simulacrum

make dist vendoring configurable

Adds a new option `dist.vendor` which allows people to decide whether to vendor dependencies for their custom distribution tarball builds. Note that our builds will not be affected, as the default for this option is the same as the previous vendoring condition from bootstrap.

Author: matthiaskrgr