testing/lsd: upgrade to 0.21.0

You can now configure lsd colors using a theme file.

Added
Added support for the MISSING / mi= dircolors variable for broken symlink targets.
Add support for theme from zwpaper #452
Update theme to support partial themes zwpaper #591
Update minimal rust version to 1.42.0 from zwpaper #534
NO_COLOR environment variable support from AnInternetTroll
Changed
Change size to use btyes in classic mode from meain
Show tree edge before name block or first column if no name block from zwpaper #468
Added icons for Perl modules (.pm) and test scripts (.t)
Add --config-file flag to read configuration file from a custom location
Clarify custom date format for date field in configuration file in the README.
Fixed
Support all strftime like formatting #532