Even more MSVC-specific warnings that evaded detection in CI

Follow up to !3950 (merged) - apparently as #7882 still isn't fixed, more warnings snuck in while the MR was awaiting review. I'm not exactly sure how, as some of the affected files haven't been touched in the intervening six days. I forgot about https://github.com/microsoft/vscode-cmake-tools/issues/3048, so initially only fixed the warnings in the launcher and its dependencies in the first MR, and in the first version of this MR, only fixed the extras in the engine. I've now built all the targets and chased away all the warnings.

I'd rather this one had a faster turnaround time so I've got more of a chance of getting the CI switched over and having warnings working properly again before more warning-generating code gets merged.