MINIFICPP-2185 Upgrade to Visual Studio 2022

[fgerlits]

The only real problem was FileSystemRepositoryTests, which relied on this STL bug: microsoft/STL#1511

In addition to that, I have

• added /MP to the command line -- I'm not sure if this does anything, but maybe;
• removed -fPIC from the command line, as it has no meaning on Windows;
• fixed some compiler warnings
• unified the Windows UTF-8 <-> UTF-16 conversions to all use the functions in UnicodeConversion.h, and moved it from extensions/windows-event-log to libminifi/utils.

For now, I have kept the VS2019 CI job and added a new VS2022 job. After MINIFICPP-2186, we can remove the VS2019 job.

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[fgerlits]

The string <-> wstring conversion functions in #1634 are better, so we should merge that PR first, and then I will merge those changes with this PR.