feat(value): add ergonomic type checking and accessor methods to JsonValue

[Aditya-9-6]

Motivation

Currently, working with JsonValue in pure Rust code requires matching on JsonValue variants for every access. Adding standard accessor and type checking methods (similar to serde_json::Value) improves developer ergonomics significantly when querying or inspecting parsed JSON data.

Solution

Added the following accessor methods to JsonValue<'j>:

• Type queries: is_null(), is_boolean(), is_number(), is_int(), is_float(), is_string(), is_array(), is_object()
• Value accessors: as_bool(), as_i64(), as_f64(), as_str(), as_array(), as_object()
• Object lookup: get(key: &str) -> Option<&JsonValue<'j>>

let val = JsonValue::parse(json_bytes, true)?;
if let Some(name) = val.get("name").and_then(|v| v.as_str()) {
    println!("Name: {name}");
}

[codecov]

Codecov Report

❌ Patch coverage is 99.12281% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
crates/jiter/src/value.rs	99.12%	0 Missing and 1 partial ⚠️

📢 Thoughts on this report? Let us know!

[codspeed-hq]

Merging this PR will degrade performance by 15.52%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

❌ 3 regressed benchmarks
✅ 67 untouched benchmarks

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	massive_ints_array_jiter_iter	564.1 µs	685 µs	-17.65%
❌	python_parse_massive_ints_array	1.1 ms	1.4 ms	-16.66%
❌	massive_ints_array_jiter_value	743 µs	845.6 µs	-12.14%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing Aditya-9-6:main (3e307d2) with main (785cf75)}