Centralize CPU interrupt channel configuration

[RhythrosaLabs]

Summary

Resolves #51 by moving CPU interrupt-channel assignments into cpu/src/kernel/config.h.

The UART, SPI, clock, and systick users now reference named configuration values, so interrupt ordering can be tuned from one header without searching individual drivers.

Validation

• git diff --check passes.
• Exact assertions confirm all six existing channel users reference the central definitions.
• Target build remains blocked in this environment because arm-none-eabi-gcc is not installed.

This change is also published on RhythrosaLabs/freetribe-studio main.

[vanasoft23]

To be honest I think this is a bad idea considering interrupt channels can have multiple interrupts assigned to it. Im not sure but bangcorrupt might have missed this fact when assigning the issue