Scala 3 fixes and improvements

[goshacodes]

Pull Request Checklist

• [x] I agree to licence my contributions under the MIT licence
• [x] I have added tests for any changed functionality

Closes

1. https://github.com/paulbutcher/ScalaMock/issues/503
2. https://github.com/paulbutcher/ScalaMock/issues/502
3. https://github.com/paulbutcher/ScalaMock/issues/170 and https://github.com/paulbutcher/ScalaMock/issues/445

Also these can be closed, since I made it work in scala 3 initially: https://github.com/paulbutcher/ScalaMock/issues/60 https://github.com/paulbutcher/ScalaMock/issues/93 https://github.com/paulbutcher/ScalaMock/issues/39 https://github.com/paulbutcher/ScalaMock/issues/499 https://github.com/paulbutcher/ScalaMock/issues/198

[goshacodes]

@barkhorn Hi, merge and publish next candidate please

[goshacodes]

P.S. review is quite simple. 1 issue - 1 commit

[barkhorn]

new release will need to wait a couple days - Thu or Fri. We used to have snapshot builds during the Travis days, might be worth getting those working again with github workflows - but need to encode the sonatype credentials somehow for that

[barkhorn]

:ship: done!