Build extra CI scenarios

[robo9k]

This runs cargo build and cargo test while dynamically linking against libmagic.
The non-extra build does the same but statically.

This also uses cargo vcpkg with cargo test and defaults for Windows.
Building without vcpkg on Windows, e.g. with MSYS2 for target x86_64-pc-windows-gnu, is untested and thus unsupported for now.

[robo9k]

Looks like the hardcoded rev = "078f3e5" in [package.metadata.vcpkg] references files that no longer exist on the MSYS2 mirrors.
Have to sneak in an unrelated-to-CI fix there.

Note that this only tests the default x64-windows-static-md community triplet for cargo-vcpkg.
For dynamic linkage, the hardcoded [package.metadata.vcpkg.target] triplet might be an issue.