use [patch] sections to specify serde_json dependency

[tvsfx]

The repo currently uses explicit git dependencies for serde_json (for example here)

This has to two disadvantages:

• It has the undesired side-effect of making these dependencies non-overridable in crates that depend on (crates in) this repo. This is similar to a =-version constraint in a Cargo.toml and can cause version collisions if dependents use a different version of serde_json (no interaction between both versions is then possible).
• It does not patch serde_json in transitive dependencies of this crate, and hence makes it so this crate uses multiple versions of serde_json (see the diffs in the Cargo.lock files for this PR)

The one small advantage is that it puts no burden on users of this crate to patch serde_json for this crate specifically, but this is easily outweighed by the disadvantages mentioned above.

Better is to use a [patch] section, so that dependencies are patched transitively (if parts of this repo are used and built stand-alone) but can still be re-patched/overridden by its clients. This PR implements this change.

[tvsfx]

CI fails because of serde-rs/json#444, which stipulates usage of serde_json > 1.0.25. Will try upating patches to the 1.0.51 branch until my patch for 1.0.128 lands and we can port to that.

[nshyrei]

@tvsfx Please resolve merge conflicts