items-can-explode flag

### The Problem

If a Wither is given a custom loot table, there is a significant chance that a skull shot just before it's death will blow up the item(s) that it drops. Nether stars are hard-coded to not explode in order to work around this issue, but it doesn't work for other items.
Similarly, creepers and ghasts can blow up items.

### A Solution

An items-can-explode flag which, when added to a region, prevent items from being exploded.

### Alternatives

Although an explosion-flags-block-entity-damage config option does exist, this prevents damage to all entities including the player and cannot be constrained to only prevent items from blowing up.

### Anything Else?

_No response_