Help the user with renv issues also from the R packages section

[marcosnav]

As a follow up to #2543, we should as well help the user from the "R packages" section.

Some latest work on this provides the user with actionable items when attempting to deploy and not having a lockfile halts the deployment.

In a similar way, it is possible to have a separate API endpoint that uses the same code already created to evaluate the current renv status and report to the "R packages" section if there is something that can be done.

[dotNomad]

Adding the "priority:high" label here as the issue this superseded (#1747) was marked as high.