refactor(embassy)!: extract arch modules as crates

[ROMemories]

Description

This PR extracts the arch modules (the manufacturer-specific modules previously found in riot-rs-embassy) as separate, manufacturer-specific crates. A major benefit of this is allowing to generate user-visible documentation for these crates, which was not possible before because (a) only one arch module could be enabled at a time and (b) it was not possible to enable any of them for documentation, because of them being manufacturer-specific.

Extracting these modules as separate crates has required to:

• Introduce a new crate (whose temporary name is riot-rs-shared-types) to break cyclic dependencies between crates/types: this new crate is depended upon by every manufacturer-specific crate.
• Revisit some types in the new riot-rs-shared-types crate to accommodate manufacturer-specific variants in enums, by introducing simple generics on them.
• Work around the orphan rules in some internal cases.
• Introduce the relevant Cargo features for individual manufacturer-specific crates. Only features that are actually useful for the crate are introduced. This introduces a slight increase in duplicated features in the tree, but has the benefit of documenting what features are actually provided by each manufacturer-specific crate.

Issues/PRs references

Depends on #391
Depends on #394

Open Questions

Testing

The following have been successfully tested in hardware (on dfaca71):

• example/gpio on nRF52840-DK, nRF5340-DK, ESP32-C6, RP2040, ST-NUCLEO-WB55RG
• example/embassy-http-server
  • on ESP32-C6, RPi Pico W with Wi-Fi
  • on nRF52840-DK, ST-NUCLEO-WB55RG on Ethernet over USB

TODO

• Clean up the circumventions around the orphan rule limitations

Future work

• Generate documentation for these new manufacturer-specific crates

Change checklist

• I have cleaned up my commit history and squashed fixup commits.
• I have followed the Coding Conventions.
• I have performed a self-review of my own code.
• I have made corresponding changes to the documentation.

[kaspar030]

Please squash & rebase. Looks fine already, I'll give it a final review by tomorrow.

[kaspar030]

I'd say this is almost good to go.
Please do the rename riot-rs-shared-types -> riot-rs-embassy-common, and move the now duplicated wifi config there.

[kaspar030]

LGTM.