ATR-2626 migrate away from actions-rs

[DannyGoldberg]

the entire actions-rs org is no longer maintained as of sometime in 2020, xref:

• https://www.reddit.com/r/rust/comments/z1mlls/actionsrs_github_actions_need_more_maintainers_or/
• Project unmaintained actions-rs/toolchain#216
  • dtolnay/rust-toolchain is the well-maintained, well-used replacement
• Node.js 12 actions are deprecated. Please use Node.js 16 actions-rs/cargo#216
  • there's not a well-loved 1:1 replacement -- https://github.com/ructions/cargo is perhaps the most popular, with only 7 stars, but we don't require the main use cases to justify using the action over plain cargo

Tested via

• passing example:
  • this branch: https://github.com/useheartbeat/heartbeat-upload/actions/runs/5755556531
  • baseline: https://github.com/useheartbeat/heartbeat-upload/actions/runs/5755557638
• intentionally failing test example:
  • this branch: https://github.com/useheartbeat/heartbeat-upload/actions/runs/5762960788/job/15623773650
  • baseline: https://github.com/useheartbeat/heartbeat-upload/actions/runs/5762952339/job/15623746476
• intentionally failing lint example:
  • this branch: https://github.com/useheartbeat/heartbeat-upload/actions/runs/5763091486/job/15624198978
  • baseline: https://github.com/useheartbeat/heartbeat-upload/actions/runs/5763085235/job/15624179660

bonus: that this branch is faster than the baseline for the overall github action in all cases 🚀