Removing appeveyor and windows integration tests with GitHub Actions, many warning fixes

[dcoeurjo]

PR Description

• Removes appeveyor
• Adds windows-latest GitHub action
• Adds a new option to enable Conan package manager at cmake step (-DENABLE_CONAN, needs Conan 1.57, super useful on windows for instance)
• when using conan, all mandatory deps (zlib, boost) are installed automatically. Few optional ones are also installed fro the windows CI bot (so far: Cairo,FFTW3)
• Fixes existing issues with find_package for optional deps.
• On GitHub action windows-latest, cache is enabled for faster build (caching folder .conan)
• Fixes few build issues on windows

Checklist

• Unit-test of your feature with Catch.
• Doxygen documentation of the code completed (classes, methods, types, members...)
• Documentation module page added or updated.
• New entry in the ChangeLog.md added.
• No warning raised in Debug mode.
• All continuous integration tests pass (Github Actions & appveyor)

[dcoeurjo]

Unless someone would like to review this one, I think I will self-merge it. Plenty of bug fixes due to the CI Debug scripts