Switch to @typestrong/ts-mockito

[Markus-Ende]

There had been quite some discussion in NagRock/ts-mockito#212, because ts-mockito seems to not be maintained anymore.

It was forked in TypeStrong/ts-mockito (npm) hoping that it will be merged back into ts-mockito but this seems not to be happening. ts-mockito was last published 3 years ago.

I tried replacing ts-mockito with @typestrong/ts-mockito in a big repo without any issues. So I propose moving to @typestrong/ts-mockito as peer dependency.