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GH-33807: [R] Add a message if we detect running under emulation (#37777)

Resolves #33807 and #37034

### Rationale for this change

If someone is running R under emulation, arrow segfaults without error. We can detect this when we load so can also warn people that this is not recommended. Though the version of R being run is not directly an arrow issue, arrow fails very quickly in this configuration.

### What changes are included in this PR?

Detect when running under rosetta (on macOS only) and warn when the library is attached

### Are these changes tested?

No, given the paucity of ARM-based mac CI, testing this organically would be difficult. But the logic is straightforward.

### Are there any user-facing changes?

Yes, a warning when someone loads arrow under emulation.
* Closes: #33807

Authored-by: Jonathan Keane <jkeane@gmail.com>
Signed-off-by: Jonathan Keane <jkeane@gmail.com>