Remove FRAMETIME return value from all FX (#5314)

* remove "return FRAMETIME" from all FX, fix timing for some FX

- all FX now render every frame, no more "speed up" during transitions

* fix missing return by adding FS_FALLBACK_STATIC macro

* add FX_FALLBACK_STATIC also to user_fx

* remove obsolete seg.next_time

usermods/Temperature/Temperature.cpp

@@ -1,6 +1,6 @@
 #include "UsermodTemperature.h"
 
-static uint16_t mode_temperature();
+static void mode_temperature();
 
 //Dallas sensor quick (& dirty) reading. Credit to - Author: Peter Scargill, August 17th, 2013
 float UsermodTemperature::readDallas() {
@@ -369,13 +369,12 @@ const char UsermodTemperature::_temperature[]  PROGMEM = "temperature";
 const char UsermodTemperature::_Temperature[]  PROGMEM = "/temperature";
 const char UsermodTemperature::_data_fx[]      PROGMEM = "Temperature@Min,Max;;!;01;pal=54,sx=255,ix=0";
 
-static uint16_t mode_temperature() {
+static void mode_temperature() {
   float low  = roundf(mapf((float)SEGMENT.speed, 0.f, 255.f, -150.f, 150.f));    // default: 15°C, range: -15°C to 15°C
   float high = roundf(mapf((float)SEGMENT.intensity, 0.f, 255.f, 300.f, 600.f));  // default: 30°C, range 30°C to 60°C
   float temp = constrain(UsermodTemperature::getInstance()->getTemperatureC()*10.f, low, high);   // get a little better resolution (*10)
   unsigned i = map(roundf(temp), (unsigned)low, (unsigned)high, 0, 248);
   SEGMENT.fill(SEGMENT.color_from_palette(i, false, false, 255));
-  return FRAMETIME;
 }