Bump cmake min version to 3.14 #3348
Description
Is your feature request related to a problem?
The current cmake minimum version is 3.10. However it is not possible to use this version to build opentelemetry-cpp as some of the cmake files, ci scripts, and dependencies rely on newer versions.
There is no test for the minimum version in ci currently.
Describe the solution you'd like
Bump the version minimum to 3.14, update cmake files/scripts to support that version, and add a test in ci.
Describe alternatives you've considered
Bump to cmake minimum version 3.16 but doing this after the new versions of googletest, protobuf, and grpc are released seems reasonable.
Additional context
Current dependencies rely on newer versions of cmake already:
- googletest requires cmake version 3.13 as of gtest v1.14
- prometheus-cpp requires cmake version 3.14 since v1.0.0
Google has bumped the min version to 3.16 on the main branches of googletest, protobuf, and grpc according to their cxx-support-matrix.