Make all visualizations that write to stdout accept an out_file argument

[karkhaz]

Currently, the dump_yaml visualization prints to stdout unconditionally.

It would be good for all visualizations that print something to be able to print it to a file. This means that we can have several sequential visualizations, each writing their output to a different file. This is useful in CI for example, where we might wish to save the file as an artifact. It also ensures that we can separate the outputs of different visualizations.

This can use the existing implementation of Outfile, where a value of - means "write to stdout".