A value-like macro binding that isn't constant should not be a static readonly field, it should be a static readonly property

This macro ([source](https://github.com/erincatto/box3d/blob/23861418d877fdd97990f35645e845e44a7eb9ec/include/box3d/constants.h#L27))
```c
#define B3_HUGE ( 1.0e9f * b3GetLengthUnitsPerMeter() )
```
generates
```cs
[NativeTypeName("#define B3_HUGE ( 1.0e5f * b3GetLengthUnitsPerMeter() )")]
public static readonly float B3_HUGE = (1.0e5f * b3GetLengthUnitsPerMeter());
```
but `b3GetLengthUnitsPerMeter()` can change during runtime.

Start with include/box3d/constants.h at the B3_HUGE definition and trace how ClangSharp generates the shown C# binding for value-like macros. Verify the generated member reflects changes from b3GetLengthUnitsPerMeter() at runtime; done means the binding is a static readonly property rather than an eagerly initialized field.

Written by the indexing model from the issue text.