Update CMake Minimum Version

[goatshriek]

The current minimum version for the project, 3.2.3, prevents it from using some CMake features that would make the build cleaner and more robust. A number of issues have been caused by this minimum version, listed below for tracking. If you come across your own problem, please document it in this issue, and it will be addressed in the next update.

CMAKE_PROJECT_VERSION is unavailable, which is a cleaner way to specify version numbers than is currently done for example in the configure headers and pkg-config support.

Google Test and Benchmark integration is hacky and brittle, as a result of FetchContent not being available.

CMAKE_PROJECT_DESCRIPTION is not available, which could make some package management tooling (such as portage) cleaner.

[emansom]

Adopting FetchContent might not be the best option on Linux platforms, as there, reusability through shared libraries is usually preferred for less duplication across software packages.