Fixed mysql not supporting offset() without a limit()

[Aethelflaed]

While working on #4245, I realised I needed a limit() call before calling offset() for mysql, and thought that was a normal behaviour.

Then I saw in the 2.0.0 changelog that there should have been a workaround for that already.

It seems it wasn't entirely tested and working, so here are the missing pieces

[weiznich]

Thanks for opening this PR

The PR that introduced this behavior was #2029. Back then we explicitly decided to not support offset without limit for mysql wherever possible as that "workaround" is really an ugly hack that should be made explicit by the calling side. Unfortunately we can only guarantee that for unboxed statements, not for boxed ones, therefore the "workaround" there. So no, this is no missing piece but an explicit design decision.

[Aethelflaed]

The PR that introduced this behavior was #2029. Back then we explicitly decided to not support offset without limit for mysql wherever possible as that "workaround" is really an ugly hack that should be made explicit by the calling side. Unfortunately we can only guarantee that for unboxed statements, not for boxed ones, therefore the "workaround" there. So no, this is no missing piece but an explicit design decision.

I'll look if it's possible to add a warning

[Aethelflaed]

It's still not possible to add a deprecated message on a trait implementation item so nothing changed since #2029.

cc @weiznich