Convert remaining structures to structure format.

Many structures in Minecraft currently exist using a structure file format that allows them to be spawned using the Structure Block, or edited in data packs to replace their composition, or provide additional variations to their structure. Structures that currently use this format include the village, shipwreck, pillager outpost, igloo, and dungeon.

However, certain specific structures do not use this format to generate. Particular examples include both the Desert and Jungle Temple, the Swamp Hut, the Ocean Monument, and the Nether Fortress. As a result, these various structures cannot be modified by data packs, unlike their counterparts that do use the structure format.

I believe these remaining structures should be converted to the structure format, both for parity, and to allow data pack creators, such as myself, the ability to modify these structures in our data packs.