Value types for representing arbitrary values in a log record.
Note: The tracing and log crates only support basic types that can be
converted to these core variants: i64, f64, StringValue, and bool.
Any complex and custom types are supported through their Debug implementation,
and converted to String. More complex types (Bytes, ListAny, and Map) are
included here to meet specification requirements and are available to support
custom appenders that may be implemented for other logging crates.
These types allow for handling dynamic data structures, so keep in mind the
potential performance overhead of using boxed vectors and maps in appenders.