feat: add toStyledString overloads for custom builder and precision

[YackerYan]

Fixes #1616

Adds two Json::Value::toStyledString overloads:

• toStyledString(const StreamWriterBuilder& builder): serialize using any builder settings (indentation, comment style, precision, etc.).
• toStyledString(unsigned int precision, PrecisionType precisionType): shorthand for controlling floating-point output, in either decimal places or significant digits. Precision above 17 is capped, same as StreamWriterBuilder.

Notes:

• The existing no-argument toStyledString() is unchanged, so the exported symbol and ABI are preserved.
• When the builder sets commentStyle to "None", the leading newline normally added for a commentBefore comment is omitted.
• Added unit tests ValueTest/toStyledStringWithBuilder and ValueTest/toStyledStringWithPrecision.

[greptile-apps]

Confidence Score: 5/5

[Medium risk] Adds precision control overloads to JSON serialization.

The PR appears safe to merge; no new actionable defect or outstanding previous finding was identified.

Summary

The PR adds builder-configured and precision-configured Value::toStyledString overloads while retaining the no-argument method.

• The latest change defaults a one-argument precision call to decimal-place mode.
• Tests cover builder settings and both explicit precision modes.

_{Reviews (4) · Last reviewed commit: "Update include/json/value.h"}

[YackerYan]

Thanks for the review! I've rebased onto the latest master and squashed everything into a single commit (4c61985). All five points are addressed:

1. Incomplete builder breaks compilation: Removed the default argument. toStyledString(const StreamWriterBuilder&) is now a separate overload, so the forward declaration in forwards.h is enough and value.h compiles on its own.
2. Existing library symbol disappears: The original String toStyledString() const; is kept unchanged, so the exported symbol is preserved. It now delegates to the builder overload with a default-constructed StreamWriterBuilder, so behavior is identical.
3. Negative precision aborts writing: The precision parameter is now unsigned int, matching what StreamWriterBuilder reads via asUInt(). Values above 17 are already capped by newStreamWriter(), so the extra std::min was removed.
4. Suppressed comments leave blank line: The leading newline is now only added when the root has a commentBefore and the builder's commentStyle is not "None".
5. New overloads lack tests: Added ValueTest/toStyledStringWithBuilder (default output with comment, commentStyle = "None", compact indentation = "") and ValueTest/toStyledStringWithPrecision (decimal places, significant digits, and capping above 17).

All 134 unit tests and the reader/writer tests pass locally (MSVC), and the changed files are clang-format clean.