I originally did not put PathPrinter into grep-printer because I
considered it somewhat extraneous to what a "grep" program does, and
also that its implementation was rather simple. But now with hyperlink
support, its implementation has grown a smidge more complicated. And
more importantly, its existence required exposing a lot more of the
hyperlink guts. Without it, we can keep things like HyperlinkPath and
HyperlinkSpan completely private.
We can now also keep `PrinterPath` completely private as well. And this
is a breaking change.
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