Unlike end portals, nether portals do not drop replaced blocks, which can result in major item loss

Discovered while testing MC-272664.

The bug

When a nether portal is generated as a result of one in the other dimension not finding a valid target, any blocks in its way are deleted outright. This includes valuable blocks such as shulker boxes.

How to reproduce

1. Create this superflat world:

   20*minecraft:stone,minecraft:shulker_box;minecraft:the_void

2. Enter the Nether without a portal:

   /execute in minecraft:the_nether run tp @s 0 64 0

3. Build a nether portal in the Nether and use it

Expected results

Four shulker boxes would not be wiped from existence by the exit portal.

Actual results

They are.

How to fix

Could be fixed in much the same way as MC-902 was: when generating a nether portal, any blocks in the way would be broken as if by a player, rather than wiped from the level.