[CMake] Set the minimum required version to 3.23

This version of CMake was released in March 2022
https://github.com/Kitware/CMake/releases/tag/v3.23.0

This version is required to use FILE_SETs, which could help towards #16327 and #18419.

Since cmake_minimum_required updates the cmake_policy from 3.20 to 3.23, we need to take care of a change that happened from 3.20 to 3.21 that leads to an error
in the CheckCompiler CMake module, so set the proper policy flag to old to avoid that error on some platforms.

Author: ferdymercury

CMakeLists.txt

@@ -4,7 +4,7 @@
 # For the licensing terms see $ROOTSYS/LICENSE.
 # For the list of contributors see $ROOTSYS/README/CREDITS.
 
-cmake_minimum_required(VERSION 3.20 FATAL_ERROR)
+cmake_minimum_required(VERSION 3.23 FATAL_ERROR)
 
 if(WIN32)
   # Set CMP0091 (MSVC runtime library flags are selected by an abstraction) to OLD
@@ -61,7 +61,7 @@ foreach(policy ${policy_new})
   endif()
 endforeach()
 
-set(policy_old CMP0116 CMP0135 CMP0144)
+set(policy_old CMP0116 CMP0126 CMP0135 CMP0144)
 foreach(policy ${policy_old})
   if(POLICY ${policy})
     cmake_policy(SET ${policy} OLD)