Rules.py misc changes

[nicopop]

I got inspired by what I said on discord in manual-core-dev channel and I went and really looked at the rules.py file
things included in this PR so far:

• Deduplicate the item_count code in checkRequireStringForArea
• Added some checks so the item_count code is not run for item that are already processed
• Added Some type anotations to make mypy happy
• Made item_count only check the last : in an item name
• Made item_count convert back to item_name if the count is an unknown string

that last point can be reverted/modified if we still want it to raise an exception instead