chore: Use faster JSON encoding library

[varungandhi-src]

scip print --json is a bit slow; this change provides a noticeable speedup.

E.g. on benchmarking against flink-1.scip.

❯ hyperfine '~/Code/scip/scip-before print --json flink-1.scip' '~/Code/scip/scip-after print --json flink-1.scip'
Benchmark 1: ~/Code/scip/scip-before print --json flink-1.scip
  Time (mean ± σ):      5.786 s ±  0.547 s    [User: 7.225 s, System: 0.861 s]
  Range (min … max):    5.499 s …  7.330 s    10 runs

Benchmark 2: ~/Code/scip/scip-after print --json flink-1.scip
  Time (mean ± σ):      3.323 s ±  0.197 s    [User: 4.294 s, System: 0.685 s]
  Range (min … max):    3.180 s …  3.870 s    10 runs

Summary
  '~/Code/scip/scip-after print --json flink-1.scip' ran
    1.74 ± 0.19 times faster than '~/Code/scip/scip-before print --json flink-1.scip'

Test plan

n/a

[varungandhi-src]

This is technically a breaking change, but scip print --json is only meant to be used for debugging, so I think this is OK. This is coming about because in scip.pb.go, the struct tags specified for protobuf's JSON encoding and the normal JSON encoding are different.

https://sourcegraph.com/github.com/sourcegraph/scip/-/blob/bindings/go/scip/scip.pb.go?L1488

	ProjectRoot string `protobuf:"bytes,3,opt,name=project_root,json=projectRoot,proto3" json:"project_root,omitempty"`

[varungandhi-src]

I changed this order as expected values are supposed to be on the LHS.