Constant VALUE_SIZE

pub const VALUE_SIZE: usize = _; // 32usize

This test is to check if the size of Value exceeds the limit.

If the size exceeds the limit, you should box the variant. Previously, the size was 24. We bumped it to 32 such that String can be unboxed.

When the with-json feature is enabled, the size of Value may exceed 32 bytes to 72 bytes if serde_json feature preserve_order is enabled as different Map implementation can be used.