[build] Optimize all of V8 on CI to speed up tests

- Python test times are unacceptably high (again), let's optimize all of V8 to
  mitigate this.
- For Windows, use /O2 to enable some ancillary optimizations that are not
  covered under -O2 by clang-cl.
- Drop superfluous parameters in coverage job
- Reduce CI log frequency to reduce excessive log size