This allows removing it from `class_db.h`, significantly reducing the amount of files
that include it transitively.
Also includes some include cleanup in `control.h` and `rich_text_label.h` done while
ensure they don't depend on `callable_mp`.
A new tab is added to the debugger that can help profile a game's memory usage.
Specifically, this lets you save a snapshot of all the objects in a running
game's ObjectDB to disk. It then lets you view the snapshot and diff two
snapshots against each other. This is meant to work similarly to Chrome's
heap snapshot tool or Unity's memory profiler.
