Fix mdspan converting constructor

The converting constructor of Std::mdspan had some errors, a mixup of element-type and layout-type. This MR fixes this and also adds a corresponding converting constructor test.

added bugfix label

requested review from @gruenich

assigned to @simon.praetorius

mentioned in merge request !1433

Should be backported to 2.10

enabled an automatic merge when all merge checks for 7c72f546 pass

merged

mentioned in commit a7da5ef8

picked the changes into the branch cherry-pick-a7da5ef8 with commit 70bd621d

mentioned in commit 70bd621d

mentioned in merge request !1523 (merged)