Split into multiple backends and add support for hid/libinput recording parsing

[whot]

This is a bit messy and there's more future cleanup possible but meanwhile this is it:

• add a Backend trait that handles the actual parsing and reading of data
• move the hidraw bits into its own backend
• add backends for libinput recordings and hid recorder recordings
• move the cprintln bits into functions on the Outfile so the backends don't need to care about individual line formatting

The latter is a bit unrelated but copy/pasting the same printf statements was getting annoying.

The goal eventually is to make the Outfile functions color-support-aware so we can fix #39

[whot]

I'm going to merge this because it works even though it's not yet as pretty as it can be. In particular, it'd be nice to have the markers only in non-colour output and rely on the color output only otherwise but that requires a bit more rework (and probably ditching owo_colors). Anyway, it does the job for now.