upgrade serde and related crates

[tdyas]

Upgrade serde and related crates:

     Locking 6 packages to latest compatible versions
    Updating serde v1.0.197 -> v1.0.210
    Updating serde_derive v1.0.197 -> v1.0.210
    Updating serde_json v1.0.116 -> v1.0.128
    Updating serde_test v1.0.176 -> v1.0.177
    Updating serde_yaml v0.9.32 -> v0.9.34+deprecated
    Updating unsafe-libyaml v0.2.10 -> v0.2.11

Note: serde_yaml is no longer maintained (as per its crates.io page). This PR does not try to move away from it.

[benjyw]

Shouldn't there be a corresponding Cargo.toml change in this PR?

[tdyas]

Shouldn't there be a corresponding Cargo.toml change in this PR?

cargo update does not do that. The newer version in the Cargo.lock is still compatible with the version pin in the Cargo.toml so no real need to bump the version requirement in the Cargo.toml.