Standardize data types

[div5252]

There are many places in the library where the data types aren't standardize, for eg. in the coordinate systems. For example, the size of long int i.e. 8 usually, varies from compiler to compiler, and so it could lead to an issue. You can see this here- https://godbolt.org/z/cEsMPP

So we should be using the std::int64_t/std::size_t by including the header file cstdint.