ARROW-10735: [R] Remove arrow-without-arrow wrapping

[nealrichardson]

Key features:

• if arrowExports.* are not modified, they are not rewritten. This means that if there are no cpp changes, then nothing gets recompiled, which makes local dev faster (when you have ARROW_R_DEV=true set)
• refactoring of codegen.R to be more consistently aware of "features" that can be flagged, like we have currently for arrow and s3 and potentially may get more of in the future with additional build-time features. Importantly, the wrapping with the fake implementation that we currently have for all functions has been encapsulated in such a way that we can choose whether to make some features always on or not.

A single commit (a963e7c) adds an if statement that effectively removes the arrow-without-arrow wrapping while still keeping S3 support optional (-2,795 lines of code).

IMO we should go with this for a while, and if there is no further problems, we can remove the ARROW_R_WITH_ARROW flags everywhere. Or if we decide to change our minds, we just remove the if statement in codegen.R, nothing else to restore.

In order to fully remove the flagging, we'd need to remove all occurrences of ARROW_R_WITH_ARROW and also the special test handling of this, which includes another environment variable that is set in CI.

[github-actions]

https://issues.apache.org/jira/browse/ARROW-10735

[jonkeane]

LGTM

[nealrichardson]

I've made ARROW-11392 for the final removal of the arrow-without-arrow flagging