Allow arrays with runtime defined rank.

[1uc]

Arrays do not need to have a compile-time constant number of dimensions (rank). There's two compile-time constant variable: https://github.com/BlueBrain/HighFive/blob/1299c556a992bea8aa03c3b75cca50560a5078b6/include/highfive/bits/H5Inspector_misc.hpp#L165-L166

It's uses seems to be mostly for input validation https://github.com/search?q=repo%3ABlueBrain%2FHighFive%20recursive_ndim&type=code

Here it's not immediately used for input validation, and there's no container near by to get he runtime-value: https://github.com/BlueBrain/HighFive/blob/1299c556a992bea8aa03c3b75cca50560a5078b6/include/highfive/bits/H5ReadWrite_misc.hpp#L132-L143

[1uc]

Marked as v3 since it requires changes to the internal inspector. Given how close we are to v3 and that users have touch this internal detail to add new containers, we might as well consider changes to the inspector as breaking changes.

[1uc]

Fixed by #938.