The general idea is to keep the 'old', C-style MEM_callocN signature, and slowly
replace most of its usages with the new, C++-style type-safer template version.
* `MEM_cnew<T>` allocation version is renamed to `MEM_callocN<T>`.
* `MEM_cnew_array<T>` allocation version is renamed to `MEM_calloc_arrayN<T>`.
* `MEM_cnew<T>` duplicate version is renamed to `MEM_dupallocN<T>`.
Similar templates type-safe version of `MEM_mallocN` will be added soon
as well.
Following discussions in !134452.
NOTE: For now static type checking in `MEM_callocN` and related are slightly
different for Windows MSVC. This compiler seems to consider structs using the
`DNA_DEFINE_CXX_METHODS` macro as non-trivial (likely because their default
copy constructors are deleted). So using checks on trivially
constructible/destructible instead on this compiler/system.
Pull Request: https://projects.blender.org/blender/blender/pulls/134771
