[R][CI] Add crossbow job for full R autobrew macOS build

[asfimport]

I have a separate nightly job that runs this on multiple R versions, but it would be nice to be able to have crossbow check this on a PR. As it turns out, the ARROW_S3 feature doesn't work with autobrew in practice--aws-sdk-cpp doesn't seem to ship static libs via Homebrew, so the autobrew packaging doesn't work, even though the formula builds and brew audit is clean.

Reporter: Neal Richardson / @nealrichardson
Assignee: Neal Richardson / @nealrichardson

PRs and other links:

• GitHub Pull Request #5613

_{Note: This issue was originally created as ARROW-6833. Please see the migration documentation for further details.}

[asfimport]

Neal Richardson / @nealrichardson:
Issue resolved by pull request 5613
#5613