Scala3 style imports

[satorg]

Removes runner.dialectOverride.allowStarWildcardImport = false from .scalafmt.conf then applies scalafmtAll.

UPD.: also re-enables "-Xsource:3" for algebraCore and algebraLaws.

[satorg]

Looks like it is failing because in #4478 the "-Xsource:3" option was disabled for algebraCore and algebraLaws with the following commit message:

Workaround binary-compatibility issues

🤔

[satorg]

Hi @armanbilge,
Do you remember by chance what was the issue with "-Xsource:3" in #4478? I re-enabled it in this PR and all the checks seem passing. Do you think it is safe to leave "-Xsource:3" enabled then?
Thanks!

[armanbilge]

Huh, that surprises me. I do have a vague recollection of the issue, I believe it related to some methods that were lacking an explicit type, and under -Xsource:3 the type inference works differently, so this would break binary compatibility. And adding an explicit type is impossible, because the binary-compatible explicit type is different for Scala 2 and Scala 3.

If CI is happy, it's probably okay now (?) but it would be really good to understand why ...

[satorg]

Yes, it is puzzling quite a bit.. I'm going to convert this Draft to a complete PR and let it stay that way for a while.
Just in order to collect more thoughts and opinions on that and allow some time for pondering all the implications.