Settle on an API for `cuda::vector`

We want to introduce `cuda::vector` so that it can serve as a drop-replacement for most user code.

Therefore it is essential, that we provide the facilities that users expect from a standard container. Recently `std::inplace_vector` was added to C++26. That is a special container in that it does not take an allocator similar to what we envision with `cuda::vector`.

We should make a decision whether we want to deviate from the API of `std::inplace_vector` or whether we just want to take it as is.

The advantage is that it is highly familiar to users and has already gone through standardization so the design is sound.
The disadvantage is that it does carry some cruft from all the standard containers with it.