Part of #9744
Removes all redundant `# -*- coding: utf-8 -*-` lines from files, as python 3 automatically reads source code as utf-8 now.
`Signed-off-by: Jonathan de Jong <jonathan@automatia.nl>`
We do this by allowing a single iteration to process multiple rooms at a
time, as there are often a lot of really tiny rooms, which can massively
slow things down.