refactor: make json value use json type

[MichaelScofield]

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What's changed and what's your intention?

instead of being backed by ConcreteDataType directly, which makes json value verbose to operate its type

also the new json type is precisely corresponding to the json value, making codes lesser error-prone

PR Checklist

Please convert it to a draft if some of the following conditions are not met.

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR requires documentation updates.
• API changes are backward compatible.
• Schema or data changes are backward compatible.

[Copilot]

Pull Request Overview

This PR refactors the JSON value implementation to use a dedicated JsonNativeType enum instead of being directly backed by ConcreteDataType. This makes the JSON type system more precise and reduces verbosity when operating on JSON types.

Key changes:

• Introduced new JsonNativeType enum with variants for Null, Bool, Number, String, Array, and Object
• Implemented bidirectional conversions between JsonNativeType and ConcreteDataType
• Updated all JSON encoding/decoding logic to use JsonNativeType internally

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/datatypes/src/types/json_type.rs	Introduces JsonNativeType enum and refactors JsonType to use it; simplifies merge logic
src/datatypes/src/json/value.rs	Updates JsonVariant and JsonVariantRef to work with JsonNativeType
src/datatypes/src/json.rs	Refactors encoding functions to accept JsonNativeType instead of ConcreteDataType
src/datatypes/src/types/struct_type.rs	Adds #[expect(unused)] attribute to metadata() method
src/datatypes/src/data_type.rs	Updates json_native_datatype() to use new conversion
src/api/src/helper.rs	Adjusts conversion logic for JsonFormat::Native

Comments suppressed due to low confidence (1)

src/datatypes/src/json/value.rs:1

• Unnecessary clone operation. The native_type() method now returns &JsonNativeType (a reference), so calling .clone() on each array item creates unnecessary allocations. Consider refactoring to avoid cloning in the loop.

// Copyright 2023 Greptime Team

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[Copilot]

Pull Request Overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

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