Copter: SMAX (slew rate) rate gain scaling should be propagated up to angle controls

On the 25-Apr-2023 dev call we discussed whether to set the ATC_RAT_RLL/PIT_SMAX parameter to 50 by default but we decided that before doing this we should enhance the response to oscillations to also lower the angle gains (ATC_ANG_RLL/PIT_P).

The issue names no files or tests. Start by locating the Copter attitude-control code that handles ATC_RAT_RLL/PIT_SMAX and ATC_ANG_RLL/PIT_P; done means the oscillation response also lowers the corresponding angle gains.

Written by the indexing model from the issue text.