Active RAM usage counter

[Brycey92]

Active RAM usage counter in firmware across all modes, similar to the exit functionality. Toggle-able via the secrets menu

[AEFeinstein]

Any sort of system monitoring is going to incur some overhead. It's also not trivial to overdraw on the screen (see #380). You'll need to be quite careful with this.

Who is this for anyway? If it's for developers, it's much better to use ESP_LOGx and specifically target where memory is measured. I did that when managing fighter sprites, for instance.

[Brycey92]

Ah yes, it would be for developers. I wasn't sure whether the emulator had similar enough memory usage to the hardware to be useful that way. If it does, we can close this

[AEFeinstein]

What we call an emulator is really more of a simulator, since it's not even trying to accurately emulate things like CPU instructions or memory management. I still stand by targeted ESP_LOGx rather than a general overlay.