[MC-200946] Item frame texture/models are in the blocks folders, despite item frames not being a block

The bug

Item frames (including glow item frames) are an entity. However, despite this, their assets exist under the "blocks" directories.

How to reproduce

Check the block assets folders in the minecraft jar file

Expected results

The item frame resources would not be there.

Actual results

They are.

How to fix

Move these accordingly:

Old location	New location
textures/block/glow_item_frame.png	textures/entity/glow_item_frame.png
textures/block/item_frame.png	textures/entity/item_frame.png
models/block/glow_item_frame.png	models/entity/glow_item_frame.png
models/block/glow_item_frame_map.png	models/entity/glow_item_frame_map.png
models/block/item_frame.png	models/entity/item_frame.png
models/block/item_frame_map.png	models/entity/item_frame_map.png
models/block/template_item_frame.png	models/entity/template_item_frame.png
models/block/template_item_frame_map.png	models/entity/template_item_frame_map.png

Further notes

On a related note, since they do use states like a block does, it may be worth changing the blockstates/ directory to states/block, and also having a states/entity directory, which item frames' definitions could be moved to.

Old location	New location
blockstates/glow_item_frame.png	states/entity/glow_item_frame.png
blockstates/item_frame.png	states/entity/item_frame.png
blockstates/*	states/block/*
items/*	states/item/*