Make AI heroes which are defending a castle to do some action and return back

[ihhub]

Preliminary checks

• I've checked that there aren't other open issues on the same topic.

Describe the problem requiring a solution

If a hero is assigned to defend a castle he stays the whole day and does nothing even if an enemy hero is not blocking a way.

Describe the possible solution

Allow the AI hero to visit some objects but always to come to the castle if there are enough move points.

Additional info

Relates to #2499