Upgrade SB build leg from Ubuntu 20.04 to Ubuntu 22.04

[mthalman]

The runtime repo is failing to build in the Ubuntu 20.04 leg of the VMR due to this error:

Commencing build of "install" target in "CoreCLR component" for linux.x64.Release in /vmr/src/runtime/artifacts/source-build/self/src/artifacts/obj/coreclr/linux.x64.Release
Invoking "/vmr/src/runtime/artifacts/source-build/self/src/eng/native/gen-buildsys.sh" "/vmr/src/runtime/artifacts/source-build/self/src/src/coreclr" "/vmr/src/runtime/artifacts/source-build/self/src/artifacts/obj/coreclr/linux.x64.Release" x64 linux clang Release ""  -DCLR_CMAKE_PGO_INSTRUMENT=0 -DCLR_CMAKE_OPTDATA_PATH= -DCLR_CMAKE_PGO_OPTIMIZE=0 -DCLI_CMAKE_FALLBACK_OS="ubuntu.20.04" -DFEATURE_DISTRO_AGNOSTIC_SSL=0  -DCLR_CMAKE_KEEP_NATIVE_SYMBOLS=true
/vmr/src/runtime/artifacts/source-build/self/src/artifacts/obj/coreclr/linux.x64.Release /vmr/src/runtime/artifacts/source-build/self/src/src/coreclr
Not searching for unused variables given on the command line.
CMake Error at CMakeLists.txt:1 (cmake_minimum_required):
  CMake 3.20 or higher is required.  You are running version 3.16.3

This happens because the minimum required version of CMake has been upgraded to 3.20. But the CMake version in Ubuntu 20.04 is at 3.16.3.

Fixing this by upgrading the version to Ubuntu 22.04 which has the required CMake version.

[MichaelSimons]

What do you think about updating the comment above the container parameters to remind folks that when updating, corresponding changes are needed in the diff pipeline?

[mthalman]

I'm actually more inclined to put such a comment next to the buildName parameter for each job. I think it's more likely to be noticed there, and more relevant positioning.