only nerf total cognition sum when reading > flashlight

[molneya]

Alternative to #36464 and #36487.

Reading and flashlight should be treated much more separately, since the flashlight skill only accounts for object visibility and repetition, but reading accounts for overlaps, high/low AR, etc. However, for certain scores with very high reading (to the point of memorisation), the skill indeed overlaps with flashlight.

This PR uses the normal strain sum exponent for reading and flashlight (for player expectations), with an extra factor on flashlight to account for the ease of adding flashlight to a partially memorised map when reading is the dominant skill.

[stanriders]

I hope this is the last one