use single macro for real sizes in unit tests

[rem1776]

Is your feature request related to a problem? Please describe.
We have multiple tests that utilize a preprocessor macro to define the real sizes (in order to test mixed precision support), but each directory uses a different macro name. Since we're adding testing for CMake, this complicates building all those test files and it would be much simpler to use a shared macro across all test files.

Describe the solution you'd like
Use a single macro to set real sizes in all the unit tests that need it.

Additional context
Came up while working on #827

[rem1776]

added with #1694