arrow

ARROW-16414: [R] Remove ARROW_R_WITH_ARROW and arrow_available()

The diff looks bigger than that because

* Sometimes those changes just resulted in reducing indentation
* I moved arrow_info() and related functions to their own file, and did the same with ArrowObject while I was there
* The way we were wrapping testthat::test_that to check whether arrow was available had a side effect of creating a closure that stored intermediate objects that we reused across tests, and that broke when I removed it.
* I didn't have styler configured correctly in vscode when I started because I had upgraded R to 4.2, so to fix what I had already committed that was unstyled, I ran `make style-all` across everything, which reformatted a bunch of unrelated code.

I tried to pull on all threads I noticed where we were doing things an unnatural way because we couldn't assume that arrow was present, but there may be more.

Closes #13086 from nealrichardson/arrow-is-available

Lead-authored-by: Neal Richardson <neal.p.richardson@gmail.com>
Co-authored-by: Jonathan Keane <jkeane@gmail.com>
Signed-off-by: Neal Richardson <neal.p.richardson@gmail.com>