Callback fixes and allow re.on_* callbacks to remove itself

[hcdd0304]

Fixes

• Calling re.on_frame while another re.on_frame is executing will cause crashes (sometimes). Reason being callback vector being reallocated/resized while being iterated
• Write a custom class for storing callback to reduce duplication

re.on_frame(function()
   if (...) then
      re.on_frame()
   end
end)

(Note (I edit): the exception is caught by lua protected call though, I can view it only when attaching Visual Studio debugger with the game)

Addition

• Add a way for re.on_* callback to opt itself out. Requested by modder ridog for their MHWilds mod

Test code:

local current_count = 0
local stop_at = 10

re.on_frame(function()
    log.info("Frame update count: " .. current_count)
    current_count = current_count + 1

    if current_count >= stop_at then
        log.info("Reached the stop count of " .. stop_at .. ". Stopping updates.")
        return re.CallbackNextAction.STOP
    end
end)