[MC-224655] Tab-completion doesn't suggests names typed after dot or slash

The bug

Although the tab-completion suggests names, when you start to type the part of that name, that is after underscore, it does not do that with dots or slashes for example in minecraft:adventure/bullseye advancement.

How to reproduce

Type or copy the following:
```
/playsound mu
```
→ Notice that in list is suggested minecraft:music.credits
Type or copy the following:
```
/playsound cre
```
→ There is suggested nothing, even though there should be minecraft:music.credits