[Pkg-rust-maintainers] Bug#1025912: rust-serde-yaml: please upgrade to v0.9

[peter green]

I looked through some of the reverse dependencies.

lintian-brush - no changes seem to be needed.
rust-alacritty builds and passes smoke test after pointing at patched alacritty-config and alacritty-terminal
rust-alacritty-config cargo test --all --all-targets --all-features passes after bumping dependency.
rust-alacritty-terminal cargo test --all --all-targets --all-features passes after bumping dependency and pointing at patched alacritty-config
rust-bat - main code built fine after bumping dependency, but one example needed a slight tweak.
rust-carapace-spec-clap - new upstream version supports serde-yaml 0.9
rust-lsd - one test fails, but I don't think it's related to the serde-json version, also waiting for chrono-humanise right now.,,
rust-rust-code-analysis-cli - already broken and not in testing.
rust-test-case - jonas package, only seems to be used for tests, further investigation needed.
squeekboard - not investigated yet.
rust-config-file - not investigated yet.
rust-treediff - not investigated yet.

I also looked at the forward dependencies, and discovered that the unsafe-libyaml
crate is needed. Blair Noctis had packaged it but it needed sponsorship. It's now in NEW.