fix: only rewrite arithmetic when targeting Aspen processors

[notmgsk]

This MR changes when the rewrite_arithmetic functionality is used. We support two translation backends:

• V1: legacy translation, which expects the client to have used rewrite_arithmetic, and does not support Ankaa (or later) processors; and
• V2: modern translation, which expects the client to have not used rewrite_arithmetic.

Thus, to bridge the gap between the transition from V1 to V2, this MR only rewrites arithmetic if the target processor is of the Aspen family. If the user requests a backend that is not supported for the target processor, a warning is emitted and the correct backend is used instead.

When Aspen-M-3 goes offline, we can remove the checks introduced by this MR and instead require that V2 is always used.

Closes #1678

Below are plots for a program that should have period 2pi. In the first, the period is much larger.

Without fix:

With fix:

[rigetti-githubbot]

☂️ Python Coverage

current status: ✅

Overall Coverage

Lines	Covered	Coverage	Threshold	Status
6874	6015	88%	87%	🟢

New Files

No new covered files...

Modified Files

File	Coverage	Status
pyquil/api/_compiler.py	55%	🟢
TOTAL	55%	🟢

updated for commit: 42bdf8b by action🐍

[kalzoo]

It's unfortunate we have to do this, but this implementation looks right, thanks. We can all look forward to reverting this when Aspen-M-3 is retired!

Description should include a summary of your approach and rationale for quick review, both now and later (when we forget about this and wonder why we did it). Plot illustration is 👍

Also, the title becomes the commit message, and this is more than just Aspen-M-3, it's any Aspen.

Approved when comments addressed 🚢