stdlib/runtime: Implement a basic parsing library

[spotandjake]

As mentioned in #2099, in the stdlib there are multiple cases where we have needed to and will need to implement parsers such as currently for url decoding, filepaths and Json, and in the future we might want to support things like TOML, Yaml and possibly other things. It would be useful if we standardized the way we do parsing in the stdlib to make maintaining these libraries easier, this would also help maintain best practices. As we probably don't want this library to be accessible from the stdlib it would probably make sense to put this in the runtime. Alternatively maybe we want to consider adding an stdlib/helpers path for things like this. My thoughts for this library are a very low level parsing framework similar to whats in the Json library, something like a full parser generator seems overkill.