Reduce, Not Reset, Cooldown when Switching Item in Main Hand

So instead of the cooldown starting from 0 again whenever a player changes the selected item in the hotbar, it either:

• starts off at half of what it originally was
• starts off at 100% if it was above 100% before.
• or both

Motivation:

• Allows players to switch between different melee weapons and do “weapon combination attacks” e.g. suddenly pulling an axe out while using a hoe to surprise someone

• Brings back quick-switching-based item usages: i.e. potions can be used without delaying the fight by a bit after using them

• Somewhat more realistic —you take more time to gather energy to strike again after striking, as compared to after putting something down to pick something up.

note: this idea was originally suggested by MC user "Zivkovic4", after which we worked on a quick draft together.