Rust sys/wrapper version out-of-tree users get can fall behind

[chrysn]

Description

Our current workflow for the Rust modules riot-sys and riot-wrappers is to use the git versions through patch.crates-io. This is convenient because it allows developers who don't want to do crates.io uploads to fix fallout of API changes. Sadly, this can also cause troubles for users:

If the version on crates.io that is published becomes incompatible with current RIOT (eg. because RIOT starts relying on the current version to be present), users who build out of tree are suddenly presented with an old Rust module on a current RIOT.

Concrete examples

An example of this happened to @SzymonKubica in #20451 (comment) (not the main issue there AFAICT, but still he had to work around it).

Plan for mitigation

I think that the best way forward is to trigger a version bump as soon as the Cargo.lock files in here are updated; no plan yet on how to do this other than asking whoever does the update (mostly me) to remember to do it.