Broken end portals affected by MC-93185 from before 25w02a not datafixed

MC-93185 was fixed in this snapshot but any worlds affected by it remain broken without an exit portal.

Analysis & Suggested Fix

• ExitPortalLocation doesn't get datafixed to the correct value if the world was generated before snapshot 25w02a. Changing the Y value from -1 to 1 manually via external tools lets you regenerate the portal by following the reproduction steps below.
  

  [media][media]

  
  However it would be best if the portal was automatically regenerated if it's detected that it's Y value is below the world bottom.

Also due to custom worlds the fix it wouldn't be as simple as if(y<1) y = 1. Instead it should be if(y<min_y+1) y = min_y+1

Reproduction Steps

• Generate a world with seed 78539955276621 in 1.21.4

• Kill the ender dragon

• Load the world in 25w02a

• Run these commands

  • /setblock 3 1 0 minecraft:obsidian

  • /setblock -3 1 0 minecraft:obsidian

  • /setblock 0 1 -3 minecraft:obsidian

  • /setblock 0 1 3 minecraft:obsidian

• Place end crystals on the obsidian blocks

Observed Results

• Nothing happens
  

  [media]

Expected Results

• The end portal would be regenerated