Proposal to update default Windows build chain to Visual Studio 2019

[Noel Grandin]

Hi

I propose that we updated our Windows builders to use VS2019 and make that our new preferred baseline.

Visual Studio 2019 is now and truly bedded down, has been through several releases, and is in daily use by at least one 
of our developers for some time.

Highlights of the VS2019 compile/build tools:

(*) AddressSanitizer support for projects compiled with MSVC on Windows.

(*) Build throughput improvements, including the way the linker handles File I/O, and link time in PDB type merging and 
creation

(*) Lots of C++ conformance fixes and improvements, including some C++20 support

Links:
https://docs.microsoft.com/en-us/visualstudio/releases/2019/release-notes
https://docs.microsoft.com/en-us/cpp/overview/what-s-new-for-visual-cpp-in-visual-studio?view=vs-2019
https://docs.microsoft.com/en-us/cpp/overview/cpp-conformance-improvements?view=vs-2019

Regards, Noel.