chore: Extract `turborepo-json-rewrite` crate from `turborepo-lib` (#11318)
## Summary
Extract the self-contained `rewrite_json` module into its own crate as
part of the ongoing `turborepo-lib` modularization effort.
- Create new `turborepo-json-rewrite` crate with `jsonc-parser`
dependency
- Re-export from `turborepo-lib` to preserve existing internal usages
- All 14 existing tests pass
## Details
This module provides JSON document mutation utilities (`set_path`,
`unset_path`) used for modifying `turbo.json` configuration files. It
has **zero internal dependencies**, making it an ideal first extraction
candidate.
The re-export pattern (`pub use turborepo_json_rewrite as
rewrite_json;`) ensures all existing internal usages continue to work
without modification.
## Test Plan
- `cargo check -p turborepo-json-rewrite -p turborepo-lib` ✅
- `cargo test -p turborepo-json-rewrite` ✅ (14 tests pass)