[R] Update ARROW_DEPENDENCY_SOURCE to default to AUTO

[asfimport]

We should make ARROW_DEPENDENCY_SOURCE=AUTO the default and then document how to install the dependencies (such that you can) using apt/yum; that will speed up source builds

Reporter: Nicola Crane / @thisisnic
Assignee: Nicola Crane / @thisisnic

Related issues:

• [R] Improve source build experience (is duplicated by)

PRs and other links:

• GitHub Pull Request #11881

_{Note: This issue was originally created as ARROW-14850. Please see the migration documentation for further details.}

[asfimport]

Nicola Crane / @thisisnic:
Issue resolved by pull request 11881
#11881