Fix parse_cargo_tree_output misclassifying dev-dependencies as host deps

[jonremy]

Fix parse_cargo_tree_output incorrectly classifying [dev-dependencies] as host dependencies when they follow [build-dependencies] for the same crate.

This causes platform-conditional features to leak across platforms in the generated BUILD files. For instance, the tokio feature taskdump that can only be enabled on linux could leak to other platforms.

Example dependency tree that triggers the issue:

;my-crate v0.1.0 (/my-crate);;
`-- ;tokio v1.49.0;bytes,full,taskdump;
[build-dependencies]
`-- ;anyhow v1.0.100;default,std;
[dev-dependencies]
`-- ;tokio-test v0.4.4;;
    `-- ;tokio v1.49.0;bytes,full,taskdump; (*)

This PR also updates surrounding code in parse_cargo_tree_output. Let me know if you'd prefer a minimal fix instead.

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[UebelAndre]

Thank you!