Async API

[jbeaurivage]

Provide APIs to use some peripherals using async/await.

HAL features

One new feature is added to the HAL: async

MSRV

This PR bumps the HAL MSRV to rustc 1.75. However everything compiles on stable.

Peripherals implemented

• Timer/Counter (TC)
• I2C
• UART
• SPI
• DMAC
• GPIO interrupts (EIC)

Todo

• Document everything
• Find best API for interrupt ownership
• Convert to new peripheral-feature system, especially brand new modules

Examples

Some examples are provided for feather_m0 (and a few for metro_m4). Some more examples will be added in time, perhaps in a follow-up PR.

Breaking changes

• The EIC drivers have a slightly new API.
• Removed wakers for sync dmac::Transfers.

[sajattack]

One example I think will definitely need testing is async_eic, I'm not 100% sure about it yet, even though it works well on thumbv6 targets.

I tested it on metro m4. It works great.

INFO  Falling edge detected
└─ async_eic::____embassy_main_task::{async_fn#0} @ examples/async_eic.rs:59
INFO  Falling edge detected
└─ async_eic::____embassy_main_task::{async_fn#0} @ examples/async_eic.rs:59
INFO  Falling edge detected
└─ async_eic::____embassy_main_task::{async_fn#0} @ examples/async_eic.rs:59
INFO  Falling edge detected
└─ async_eic::____embassy_main_task::{async_fn#0} @ examples/async_eic.rs:59
INFO  Falling edge detected

[jbeaurivage]

Branch is rebased on top of #780.

[jbeaurivage]

Note to reviewers: please use "Rebase and merge" to preserve the git history.