Powder snow buckets render powder snow in sulfur cubes; water and lava buckets do not

Relates to MC-64222 and MC-195271.

If you summon a sulfur cube which has a powder snow bucket in its body slot, then powder snow will be rendered inside of it. This is because the powder snow bucket is intrinsically linked to the powder snow block as its equivalent item form (hence why they are dropped from falling block entities, or displayed in the Superflat menu, or in previous versions, dropped by endermen holding powder snow).

Similarly, water buckets and lava buckets are linked to water and lava in much the same way. However, they are not displayed inside of sulfur cubes which have buckets equipped. This constitutes a functional inconsistency.

To reproduce, run these commands and observe the created entities:

• /summon sulfur_cube ~ ~ ~ {Size:1,equipment:{body:{id:"water_bucket"}}}

• /summon sulfur_cube ~ ~ ~ {Size:1,equipment:{body:{id:"lava_bucket"}}}

• /summon sulfur_cube ~ ~ ~ {Size:1,equipment:{body:{id:"powder_snow_bucket"}}}

Expected results: the water bucket sulfur cube would contain water, the lava bucket sulfur cube would contain lava, and the powder snow sulfur cube would contain powder snow.

Actual results: the water bucket sulfur cube does not contain water and the lava bucket sulfur cube does not contain lava. The powder snow sulfur cube does contain powder snow.