Add Path::display_lossy() and display_escaped() methods

[sunshowers]

Currently Path has:

• a single display() method which converts any invalid UTF-8 bytes to REPLACEMENT CHARACTER (U+FFFD)
• a Debug impl that always adds quotes and escapes invalid UTF-8 bytes

This can result in some confusion because people that "just want to print a path" may end up inadvertently producing lossy output.

It would be great to:

• add a display_escaped() method which is similar to the Debug impl if there are invalid UTF-8 bytes, or the current display() impl if there aren't. In other words:
  • if there are invalid UTF-8 byte sequences, it adds quotes and escapes those byte sequences
  • if not, then it doesn't add quotes.
• rename display() to display_lossy() (and perhaps deprecate display() in a new Rust edition?)

cc @Manishearth (who requested I file this), @m-ou-se

[jyn514]

(and perhaps deprecate display() in a new Rust edition?)

Deprecations don't need to be tied to editions, only breaking changes.

[Manishearth]

a single display() method which converts any invalid UTF-8 bytes to REPLACEMENT CHARACTER (U+FFFD)

Worth noting: this is its current behavior, it is not documented as such, and it is allowed to differ between platforms