Add Tier 3 support for 64-bit Raspberry Pi to PEP 11

[savannahostrowski]

Hey folks - I recently opened python/peps#4647 and would like to offer to support 64-bit Raspberry Pi as a platform. Right now, PEP 11 already states support for 32-bit RPi via @gpshead. I've set up a buildbot for 64-bit RPi and have a device available for testing, so I'm committed to maintaining support for this platform following the Tier 3 requirements.

I don't expect this to be terribly controversial given the existing 32-bit support, but I wanted to get formal approval from the Steering Council before merging. Please let me know if you have any questions!

[StanFromIreland]

Yay! Also note that there are two other ARM64 raspbian builders, pablogsal-rasp and stan-raspbian, are stable and all green (except a little warnings issue, see python/cpython#139805).

[pablogsal]

We will discuss this formally tomorrow (but I don't see any reason why this won't go ahead).

[gpshead]

approved.

[savannahostrowski]

Thank you, folks!