feat(turborepo): Root turbo.json parsing (#5228)
### Description
Implements root turbo json parsing with conversion from a `RawTurboJson`
as deserialized from JSON to a `TurboJson` with a
`BookkeepingTaskDefinition`. Includes synthesis from package.json file.
### Testing Instructions
Adds testing for deserialization and synthesis.
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Co-authored-by: --global <Nicholas Yang>
