Upgrade Linux & Windows CI fleet (#2090)

- Migrate all machines from c2-standard-30 to c3d-standard-30
- Grow Linux pool from 100 to 200
- Grow Windows pool from 30 to 60
- Upgrade image creation machine from c2-standard-8 to c3d-standard-8

Progress towards
https://github.com/bazelbuild/continuous-integration/issues/2089
2 files changed