Structure names allow trailing dots for folder names

The bug

Continuation of MC-131152; forgot that Windows does not allow trailing dots in folder names.

Structure blocks allow structure names containing folder names with trailing dots. This is not allowed for Windows. While Minecraft is apparently most of the time able to create the parent folders (sometimes leaving out the dots), it looks like it nearly always fails creating the structure file. Additionally it would be rather difficult for users to delete these folders manually, see this StackOverflow question.

How to reproduce

1. /setblock ~ ~ ~ structure_block[mode=save]{mode:"SAVE",name:"a.../b"}
   

2. Open the structure block GUI and click "SAVE"
   → Under Windows it should say "Unable to save structure", however it actually created a folder a in the generated/minecraft/structures directory of the world