Lock MSVC compiler version

Today, we install Microsoft.VisualStudio.Component.VC.Tools.x86.x64 into our build tools. This includes the latest version of the C++ compiler. That moving target causes several types of problems:

A few VC versions are not compatible with UE. There's a risk that future VC versions suddenly fail as well.
VC obj/lib/pdb files are forward compatible, but not necessarily backward compatible. If the prebuilt Engine version uses a new VC version, then anyone who wishes to use that version and build Game code must be on that VC version or a newer one. Because of this, VC upgrades in the build system force developers to update the VC version on their workstations.
Managing the build system becomes more difficult; if we want to fix a specific problem with the Windows builders, and this requires rebuilding VM images / Docker buildtools images, then the rebuild will also update VC to the latest version. This forces the above knock-on effects. It's preferable to have explicit control over the VC version.

Locking the VC version is reasonably straightforward: We should replace the VC tools Workload with the necessary components instead - but make sure to lock any components that we can. See the Workloads and Component IDs for reference.

We should probably standardize on a VC version for now. v16.11 is the final servicing release for MSVC 2019, we should pick that.

Note, this will only lock the C++ compiler versions, and will lock major+minor, but not servicing release. Other bits (like C# compiler) remain a moving target I think. To lock that, we would need to save the exact boostrap installer (vs_buildtools.exe) used - but MS only makes the most recent publicly available, older versions are allegedly possible to download from my.visualstudio.com but that requires logging in first. The bootstrap installer furthermore supports a --channelUri argument, through which we could force a different installation manifest -- but again, where do we get older manifests?

Another option would be to regularly fetch the vs_buildtools.exe package and create an archive of offline installers that way. Still, however... this is silly.

falldamagestudio / UE-Jenkins-BuildSystem

Lock MSVC compiler version #57