Spawning a structure with waterloggable blocks next to or inside a water source will waterlog the structure

The bug

When loading a structure containing waterloggable blocks (which are not waterlogged) next to or inside a water source, the blocks inside the structure become waterlogged.

This is related to MC-130584, but not the same issue since MC-130584 is about water sources inside the structure spreading; while this report is about external water sources not being replaced and spreading inside the structure.

Note: In some cases this behavior might be desired, e.g. for shipwrecks. Maybe the structure file should support specifying whether a block removes water or becomes waterlogged onces loaded next to / inside water.