Add `write_verbose` parameter to VespaEvaluator (like VespaMatchEvaluator)

[PeriLara]

The MatchPhaseEvaluator in pyvespa supports a write_verbose parameter, which is very useful for debugging and analysis. However, the VespaEvaluator does not currently offer this option.

Btw: I’ve already implemented this for my own use case and can share the code or a PR if helpful.

[thomasht86]

Hi @PeriLara!
If you already have this implemented, a PR is very welcome. :)