Lua: Allow using Lua to manipulate effects and define requirements

[XHawk87]

Is your feature request related to a problem? Please describe.
Lua scripts can be very useful, but currently they are based around creating handlers for emitted signals and adding behaviour to occur at these moments. Effects on the other hand are used to modify existing functionality by feeding data back to something that is processing a behaviour based on a set of rules. I would like to be able to leverage the power of Lua for effects also, and define more advanced requirements for effects.

Describe the solution you'd like

• Add an effects.create(name, type, value, multiplier, reqs) function to define an effect.
  • The requirements can be a function name, similar to how signal.connect() works, that accept the contextual parameters and returns true or false for if the effect should be applied
• Add an effects.remove(name) function to remove an effect.
• Add an effects.define(type) function for defining new custom effect types that we can use with effects.X_bonus() functions in signal handlers.

Additional context
Discussion thread in Discord

[lmoureaux]

Should keep #2326 in mind, I think effects in general are reaching their limit in terms of flexibility.