Add support for cel expressions to scalar types

[Alfus]

Since protoyaml depends on protovalidate, cel-go is already a dependency. Scalars that do not trivially parse are passed through cel to see if they can be evaluated. The tag !cel can be used to force cel evaluation for strings. Similar to protovalidate, this and now are bound.

[Alfus]

protoyaml is not protojson and you cannot fuzz them like that for many reason.