Migrate from bisync to maybe-async

[Gioelio]

Due to a yanked version of bisync, the available solutions (I found) were:

• Vendor bisync: Include a vendor/bisync folder by cloning the project. This would lose author support and macro updates, while any bug fixes would require updating every driver.
• Fork bisync into a new crate: This avoids updating every driver individually and reduces duplicated code, but still lacks upstream updates.
• Migrate from bisync to maybe-async: Replaces the dependency entirely and get community support.

This PR implements the third option. If approved, the remaining steps are:

1. Release a new major version of both st-mem-bank-macro and st-mems-bus.
2. Update all sensor drivers (a straightforward change; once the major releases are published, I will open the necessary PRs).

If anyone has a better proposal or solution, feel free to share it here.