Update the min required CMake version to 3.10

This change also removes policy settings that are now already set to
`NEW` by default. There are still two remaining policies that were
introduced in CMake > 3.10, so I left those, and documented the CMake
version they were introduced in so we know when we can later remove them
(when our min version advances beyond that).

The min CMake version supported by Protobuf is documented here:
https://github.com/google/oss-policies-info/blob/main/foundational-cxx-support-matrix.md

PiperOrigin-RevId: 511897379

CMakeLists.txt

@@ -1,29 +1,18 @@
 # Minimum CMake required
-cmake_minimum_required(VERSION 3.5)
+cmake_minimum_required(VERSION 3.10)
 
 if(protobuf_VERBOSE)
   message(STATUS "Protocol Buffers Configuring...")
 endif()
 
-# CMake policies
-cmake_policy(SET CMP0022 NEW)
-# On MacOS use @rpath/ for target's install name prefix path
-if (POLICY CMP0042)
-  cmake_policy(SET CMP0042 NEW)
-endif ()
-# Clear VERSION variables when no VERSION is given to project()
-if(POLICY CMP0048)
-  cmake_policy(SET CMP0048 NEW)
-endif()
 # MSVC runtime library flags are selected by an abstraction.
+# New in CMake 3.15: https://cmake.org/cmake/help/latest/policy/CMP0091.html
 if(POLICY CMP0091)
   cmake_policy(SET CMP0091 NEW)
 endif()
-# Honor visibility properties for all target types.
-if(POLICY CMP0063)
-  cmake_policy(SET CMP0063 NEW)
-endif()
-# option() honor variables
+
+# option() honors normal variables
+# New in CMake 3.13: https://cmake.org/cmake/help/latest/policy/CMP0077.html
 if (POLICY CMP0077)
   cmake_policy(SET CMP0077 NEW)
 endif (POLICY CMP0077)