ci: move to buildjet (#6656)

## Description

Moves CI runners to buildjet from github.

## Benchmarks

|         | before | after |
|---------|--------|-------|
| total   | 6823   | 4815  |
| slowest | 1004   | 717   |

Overall, %30 faster CI times, ~5 minutes removed for each PR in slowest
run (e2e testing).