bump minimal CMake version

[StrikerRUS]

According to the following discussion: #3405 (comment).

CMake < 3 is very-very old (in terms of their frequent releases). With 3.0 it will be possible to check API docs easier at least (docs for < 3 are hiddedn deep at their site and not structured).

[jameslamb]

I don't know enough about the possible impact, so I don't think my review should count as a ❌ or ✅

But I do want to add for other reviewers that, specifically, cmake 3.0.0 was released in December 2018: https://github.com/Kitware/CMake/releases/tag/v3.0.0

[StrikerRUS]

@jameslamb

But I do want to add for other reviewers that, specifically, cmake 3.0.0 was released in December 2018: https://github.com/Kitware/CMake/releases/tag/v3.0.0

Oh, please don't be confused by that info! Actually, CMake 3.0.0 was released June 10, 2014: https://blog.kitware.com/cmake-3-0-0-available-for-download/.

Seems the thing is that Kitware created their helper bot kwrobot in December 2018 and it pushed all old releases of CMake in one day from their main GitLab repo.
https://github.com/Kitware/CMake/releases?after=v3.11.0

[github-actions]

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