[Feedback needed] Stance switching changes, part II

[akortunov]

This is a continue of #1405.
But I am not sure if we will fix a new behaviour or revert it.

This PR is for the first case for now.
Summary of changes was made:

1. Fixed regression - bug #4050
2. Player is allowed to interrupt attack by using Toggle Weapon key, but only when Attack button is pressed, and actual attack is not triggered yet (starting the down-swing, or releasing the arrow), as Chris Robinson suggested in bug #4051 thread.
3. Do not allow to equip probes and lockpicks during attack
4. Do not allow to unequip weapons via inventory during attack
5. Reset player attack animation when unequip weapon or tool from inventory.

Note: to implement spellcast interrupting, we should check if a "start" key from "spellcast" animation group is played somehow.