Rename ILevelEditorSaveManager->GetLevelData to GenerateLevelDataFromScenery

[seannowotny]

Is your feature request related to a problem? Please describe.
As far as I can tell this method's common implementation is the generation of new LevelEdtorSaveData and it doesn't actually get an already existing instance of LevelEditorSaveData.

Describe the solution you'd like
Rename to GenerateLevelDataFromScenery

Describe alternatives you've considered
Idk, I'm sure there are better names than "[...]FromScenery"

Additional context
At first, I was incorrectly using this method, because I assumed that it would return already present LevelEditorSaveData.