Extract the Printers into munit-diff

[msosnicki]

In the #756 munit-diff was extracted, so that it can be used outside of munit context, as it is a very useful micro library.

The diffing mechanism is based on class Diff(val obtained: String, val expected: String), where a string representation of a datatype is expected. It is optimized for the Printers, which are currently in munit module (for toString it doesn't work as nicely, in munit it is merely a fallback mechanism if Printers do not reveal any difference).

I can work on extracting it into munit-diff, but wanted to ask for green light here, maybe there are some gotchas that I missed and it was left out on purpose.

[tgodzik]

I don't remember any issues, but maybe @majk-p does? I think we just wanted to extract the smallest possible part.

[majk-p]

Cant tell for sure, but likely it was due to Printers dependency on munit.Clue, which we didn't want to include in munit.diff.

[msosnicki]

I'm closing this issue, turns out there is an ongoing effort to have the pretty diffing baked into weaver as part as ongoing migration to typelevel.