Migrate from `serde_yaml` to `serde_yml`

[FlyinPancake]

As of the 25th of March serde_yaml is not maintained

There is an active fork by the name serde_yml https://github.com/sebastienrousseau/serde_yml

[justin-robinson]

That fork is archived https://github.com/sebastienrousseau/serde_yml

[wyatt-herkamp]

https://crates.io/crates/serde-saphyr is newer but maintained.

[lmmx]

I went with serde_norway in the figment2 fork, see:

• refactor: rely on serde_norway crate; deprecate serde_yaml lmmx/figment2#14
• serde saphyr lmmx/figment2#13
• chore: replace serde_yaml with serde_norway lmmx/figment2#8

and comments in this repo on #154 (comment)

Better choice than serde saphyr lmmx/figment2#13 which would add new dependencies and so be more disruptive