Implement "rummage through container" activity

# Is your feature request related to a problem? Please describe.
Right now when you grab something from a container, it just removes the moves immediately. Theoretically it could take half a minute to rummage through a container in particularly unfavorable circumstances, so being able to cancel this action is quite important.

# Describe the solution you'd like
Implement a new activity with the new activity actor infrastructure.

# Describe alternatives you've considered
none, this is pretty straightforward imo

# Additional context
As far as complexity for new features go, this is pretty straightforward. The obtain cost of an item is pretty easy to get if you have the item_location, and the activity doesn't have to do anything until it completes. the activity should start when the player tries to wield, drop, wear, activate, etc. an item from a container that you need to dig out, so it definitely will be an activity the player uses quite often.

Start by tracing the new activity actor infrastructure and the item-location obtain cost used when taking items from containers. Check the wield, drop, wear, activate, and related item actions to identify where rummaging should begin. Done means container retrieval takes an interruptible activity that completes the item action only after the required obtain cost.

Written by the indexing model from the issue text.