enhancement: Renewing biome (1.18+) options to improve natural mob spawning

[waseric]

1.17 and beyond have offered a number of new biome options. In keeping with the idea of avoiding redundant biome options, please consider this analysis, which attempts to maximize natural passive mob spawns.

Missing naturally spawned mobs: axolotl, dolphin, pufferfish, tropical fish, goat, llama, polar bear.

Proposal to add opportunity for naturally-spawning mobs

Change “Ice Plains/Ice Flats” to “Snowy Plains”.
--Snowy Plains support spawning of polar bears, rabbits, & strays.
**1.19 cold frogs

Change “Plains” to “Savanna Plateau”.
--Savanna Plateau supports spawning of sheep, cows, horses, donkeys, and llamas. (Savanna is the only biome where horses & llamas can both spawn.)
**1.19 warm frogs

Change “Dark Forest Hills” to “Lush Caves”.
--Lush Caves biome supports axolotl and tropical fish spawning.
**1.19 temperate frogs

Change “Ocean" biome to “Lukewarm Ocean”.
--Lukewarm Oceans support spawning of cod, squid, dolphin, pufferfish, and tropical fish.
**1.19 temperate frogs

Add “Snowy Slopes”.
--Snowy Slopes supports spawning of goats and rabbits.
**1.19 cold frogs ??? 1.19 allay

Later - Add “Deep, Dark”.
--Deep Dark supports spawning of the warden.

Notes: The allay will only spawn naturally in pillager outposts (in cages) or woodland mansions (in jail cells). We have plenty of biomes that could support pillager outposts. Would it be possible to add the allay-spawning functionality somehow, such as when a player builds the dark oak cage in an appropriate biome?