Add msrv1411 feature to pin once_cell to version =1.14

[notmandatory]

This is a bit of a hack, but if we make the pinned version of once_cell an optional feature, then only downstream projects that need the older version can opt-in to it by enabling the "msrv1411" feature. For example if I do this:

[dependencies]
hwi = { path = "../rust-hwi", features = ["msrv1411"] }

Then cargo update will set the Cargo.lock version of once_cell to 1.14.0. But if I don't include the feature:

[dependencies]
hwi = { path = "../rust-hwi" }

Then when I do cargo update the Cargo.lock version of once_cell is changed to 1.17.1.

I'm not in love with the feature name msrv1411 if you like this approach and have any better ideas.

[notmandatory]

I think CI is failing for unrelated reasons 😢

[danielabrozzoni]

Omg thank you! This works perfectly. I just tested it with tauri and it works as intended :)
The CI is failing because of the ledger dockerfile, same issue we had on bdk. I'll merge a PR fixing it, then can you rebase on top of it?

[danielabrozzoni]

ACK 056422d