This commit adds support for 'parent-project' functionality, which is
used by the [lein-parent][1] project. `:parent-project` is expected to
specify a single dependency, under the `:coords` key. Two notable
changes have been made to facilitate this:
1. `extractFromVectors` allows the vector dimension to be specified.
   This was previously assumed to be 2, but 1 has now been added to
   support single "bare" dependencies. I'm not aware of anything in
   the Lein ecosystem that would mandate values other than 1 or 2.
2. `collectDeps` accepts an options object for specifying whether the
   deps are nested (dimensions = 2) or not (dimensions = 1). It also
   allows specifying the `depType` explicitly, so we can have the
   relevant dependency at the path `[:parent-project :coords]` be
   labelled `parent-project`, rather than the less descriptive
   `coords`

[1]: https://github.com/achin/lein-parent

Relates to
renovatebot#7815