Print file paths for file descriptors

It is similar to `strace -y`. We need a special type for file descriptors and use a special mode to change its output from integer values to mapping them to the target file paths

Start by tracing how hatrace currently represents file descriptors and formats their integer output. Compare the requested behavior with strace -y, then identify the appropriate descriptor type and output mode; done means descriptors can be rendered as target file paths while the existing integer output remains available.

Written by the indexing model from the issue text.