(partially) removing core peripherals from RTIC context

[romancardenas]

As discussed in the previous meeting, now that RTIC v2 targets multiple architectures, some items seem too biased toward Cortex-M microcontrollers.

One of these elements is rtic::export::Peripherals. For instance, the RISC-V architecture does not have a common set of peripherals, and the current successful ports (#733 or greenlsi/rtic) end up re-exporting the device peripherals twice.

The main options we discussed to tackle this issue are:

1. Leave rtic::export::Peripherals as () when not needed.
2. Feature-gate the core peripherals of the context so it is only active when it makes sense.
3. Completely remove core peripherals from RTIC.

It would be nice to have a discussion about this topic. Personally, I'm inclined to the third option, as we would keep a common interface for all the targets. However, it may break already working examples/projects.

[korken89]

I think we can remove it. It's only a rename is cortex-m peripherals, and we can use it's full name instead.

[AfoHT]

Now with the awesome work in #733 merged, how should we go about this? Breaking change if we remove it altogether, but it would be cleaner :+1:

[romancardenas]

I'm currently working on a PR for adding support to RISC-V targets over the SLIC. I hope to be done this week. Maybe I can add this change to the PR and discuss there.

[romancardenas]

PR opened: #815