feat(riscv-rt): dedicated trap regions

[gibbz00]

Builds upon:

• RFC: Templated Linker Scripts #317
• docs(riscv-rt): make feature flag descriptions more succinct #318
• riscv-rt: organize trap section #320

Remaining

• I'm a bit lost on how to deal with LMA/VMA. esp-hal seems to just work
  without specifying any AT > REGION_TEXT, nor any loading from LMA to VMA in
  the init assembly. Does anyone know how come? @MabezDev? (Apologies for the ping.)
• Use a specific region, i.e. REGION_TRAP, or a more general one, ex. REGION_TEXT_FAST?
• Bike-shed feature flag and region names.

[MabezDev]

I'm a bit lost on how to deal with LMA/VMA. esp-hal seems to just work
without specifying any AT > REGION_TEXT, nor any loading from LMA to VMA in

It works in esp-hal because the elf isn't directly loadable/executable, we use a tool (espflash/probe-rs) to convert the elf to a format the ROM boot loader understands (https://docs.espressif.com/projects/esp-idf/en/stable/esp32/api-reference/system/app_image_format.html), and fills in the load addresses for the various sections. At least, that's my recollection, I haven't touched these parts in a while 😅.

[gibbz00]

Ok, thanks for pointing me in the right direction 😊 Closing this for now as I've realised that I want to explore some alternative ways forward.