Error chaining tweaks

[olivroy]

Just a little proof of concept. Addresses #1956 (comment)

With the usage of cli, the error messages have become a little bit more verbose.

However, I believe that usethis error messages are usually very clear, and the error trace is rarely needed.

This PR adds a default of call = NULL for usethis errors.

I overrode this default where I felt like it would be useful.

Also used call = caller_env() where it felt appropriate.

So for example, before if you called use_package_doc() on a non-package project. You'd get Error in check_is_package()

# before with project
use_package_doc()
#> Error in `check_is_package()`
#> Error message...

# with this PR
use_package_doc()
#> Error in `use_package_doc()`
#> Error message ...

I still consider this a bit incomplete, but thought I'd share in case you had some work started on this.