New postUpdateOption - cargoUpdate

[rarkins]

Describe the proposed change(s).

A new postUpdateOption cargoUpdate which runs cargo update after any Cargo artifacts updating (kind of similar reasoning as go mod tidy for go).

Describe why we need/want these change(s).

For those who pin their dependencies in particular, this would mean the lock file is always refreshed to latest transitive dependencies.

We should make sure to note the downsides/reasons you don't want to do this though:

1. This may also result in bumping/upgrading of direct dependencies too (e.g. if constraints are in use in Cargo.toml)
2. This will also result in "unrelated" changes in the lock file. e.g. the PR is for upgrading direct dependency A, but also a lot of transitive dependencies of B are upgraded too, and it changes behavior or breaks the build unrelated to A