make hotend PIDTEMP optional in PID_autotune

[ellensp]

Description

Presently void Temperature::PID_autotune(const celsius_t target, const heater_id_t heater_id, const int8_t ncycles, const bool set_result/*=false*/) assume a hotend exists and has pid values if anything has pid enabled.

If you set the following in Configuration.h

#define TEMP_SENSOR_0 0
#define PIDTEMPBED

PIDTEMP is auto undefined as it should be but PID_autotune assumes otherwise

resulting in errors:

Marlin/src/module/temperature.cpp:822:106: error: 'WATCH_TEMP_PERIOD' was not declared in this scope
       const uint16_t watch_temp_period = PER_WATCH_CBH(WATCH_CHAMBER_TEMP_PERIOD, WATCH_BED_TEMP_PERIOD, WATCH_TEMP_PERIOD);

Marlin/src/module/temperature.cpp:823:111: error: 'WATCH_TEMP_INCREASE' was not declared in this scope
       const uint8_t watch_temp_increase = PER_WATCH_CBH(WATCH_CHAMBER_TEMP_INCREASE, WATCH_BED_TEMP_INCREASE, WATCH_TEMP_INCREASE);

Marlin/src/module/temperature.cpp:824:108: error: 'TEMP_HYSTERESIS' was not declared in this scope
       const celsius_float_t watch_hysteresis = PER_WATCH_CBH(TEMP_CHAMBER_HYSTERESIS, TEMP_BED_HYSTERESIS, TEMP_HYSTERESIS),

Marlin/src/module/temperature.cpp:835:62: error: 'hotend_max_target' was not declared in this scope
     if (target > PER_CBH(CHAMBER_MAX_TARGET, BED_MAX_TARGET, hotend_max_target(heater_id))) {

Marlin/src/module/temperature.cpp:809:70: error: 'temp_hotend' was not declared in this scope
     #define SET_CBH(F,V) PER_CBH(temp_chamber.F = V, temp_bed.F = V, temp_hotend[heater_id].F = V)

Requirements

#define TEMP_SENSOR_0 0
#define PIDTEMPBED

Benefits

Builds as expceted

[ellensp]

Please check thoroughly, It seems correct but it's after midnight and my brain has turned into a pumpkin