feat(safety): shutdown interrupt

[t-bre]

Description

An interrupt triggered by the shutdown pin should cause the system to stop running in a safe way.

Requirements

• [x] Set up pin change interrupt in STM32CubeMX and re-generate code.
• [x] Create interrupt handler, make sure it is triggered by the pin change.
• [x] move ISR to where all the globals are (app_threadx.c)
• [x] add intermediary function for checking system is RTD before registering a critical fault
• [ ] Add testbench to allow shutdown to be triggered from user button pin, but only after the RTD procedure has completed.
• [ ] add stop functions to ts controller and driver control
• [ ] vcu shutdown function

[t-bre]

@Scaniox do you know yet which pin the interrupt will be on? It would be good to know so I can add it to the schematic / PCB.

[Scaniox]

At the moment I have it assigned to PF1; that is just what was there from the previous implementation, and I'm working with it assuming there is some reason for it being that pin and haven't changed it.

[t-bre]

Great thank you, I don't think there was any particular reason other than the pin being unused but we'll leave it there.