Concrete playback tests could include more information

[adpaco-aws]

Requested feature: A user trying the concrete playback feature for the first time has had problems interpreting its output. They suggested that we add more information like variable names or at least line numbers to each of the inner Vec<u8> we generate for each value.
Use case: There is nothing special about this use-case. The user has tried the feature for the first and had to do an effort to interpret the output.
Link to relevant documentation (Rust reference, Nomicon, RFC): N/A