Powering a Servo: Do I need a separate power source?
Wherever possibe use a seperate power supply.
(We do in a 4kg robot)

Use a proper noise filter if you must share a power source. An isolated DC-DC converter to supply the electronics is very effective (active filter).

Opto-isolate from the MCU to servo power amplifier.

It's the rule in industrial, where reliability matters.

Never share grounds.