Change `tactic_feedback` in agent to `SearchState`

[lenianiva]

As pointed out in #37

[sorgfresser]

Closed with #43 I think?

[lenianiva]

Closed with #43 I think?

On the mainline the agent still uses GoalState: https://github.com/lenianiva/PyPantograph/blob/605fbd0bd7252ec9b567c151ddd74efcae36623f/pantograph/search.py#L87

[lenianiva]

I can't believe I still haven't closed this issue. Maybe we need to systematically upgrade the search agent so it can handle custom feedback.