Enhance the periodic logging to help understand memory usage

[Garanas]

Description of the proposed changes

Removes the sim-based game time logger. Introduces a ui-based game time logger. This allows us to make the logging more relevant by including the session time and the heap usage.

Testing done on the proposed changes

Start a game and observe the log. It should contain entries such as:

• DEBUG: Session time: 00:35:01 Game time: 00:09:33 Heap: 288.0M / 253.2M

Additional context

It's also a great reminder to take a break as a developer when the session time reaches more than two hours. This is a common feature in games such as the Anno series which we now make available for developers. Time to stretch those legs!

Checklist

• [x] Changes are annotated, including comments where useful
• [ ] Changes are documented in the changelog for the next game version

[Garanas]

@lL1l1 and/or @MrRowey would either of you have time to review this? I'd like this to be included so that the AI developers (and zhangm18) have more to work with when they try to understand where all the memory is going to.