Fix modifiers affecting player entity following ModifiersManager component in rP22767

Modifiers affecting the player entity itself were not applying correctly.
The reason was that the cache was not correctly reset.
Adds a regression test.

Reported By: Minohaka

Tested By: Minohaka

Refs #5572 (probably fixed but kept open for verifiation).

Differential Revision: https://code.wildfiregames.com/D2236