Integrate ARM Runners

[vibhoothi]

These runners were commissioned many years back with frontend exposing arch64 as an option, but we never had a backend integration for them.

The runner is 160c, 1005G RAM, so we could start with 112c to match all other runners in terms of vcpus

Main Beta changes: https://github.com/xiph/awcy/pull/360 {Dockerimage update + build support for rav1e}

[vibhoothi]

Do not merge yet,

We would need another logic to avoid using arm runners for all other workers.

[vibhoothi]

Revive based on https://github.com/xiph/rd_tool/pull/119