Proposal to Update Minimum CMake Version to 3.22

[Kevin Kofler]

David Redondo wrote:
> FWIW Frameworks Qt minimum is still 6.5 and will be 6.6 once 6.9 releases.

So, since both Qt 6.5 and 6.6 support CMake >= 3.16, that rather speaks 
against requiring a newer CMake version in KDE Frameworks at this time.

As long as there is no concrete functionality added in CMake 3.17 to 3.22 
that is needed, I do not see a good reason to desupport 3.16 to 3.21 just 
yet.

The removal of CMake < 3.5 compatibility support in CMake 4.0 is also no 
good reason. It would be one if the current minimum required version were 
below 3.5, but 3.16 is above 3.5 (in version number arithmetic).

        Kevin Kofler