[SC-38521](https://app.shortcut.com/tiledb-inc/story/38521/update-libmagic-and-use-the-upstream-vcpkg-port)

Split from #4553.

This PR updates libmagic to version 5.45 and switches to using a vcpkg
port closer to the upstream one, which we can easily consume with
find_package(unofficial-libmagic) since microsoft/vcpkg#35274.

One complication is that the upstream port builds libmagic with its
official autotools-based build system, which is significantly slower on
Windows (on Linux it builds pretty fast). I tried to upstream the
CMake-based port I had added in #4119, but the PR was rejected.

Apart from binary caching, there is unfortunately nothing we can do
about the build performance regression. We could maintain the
CMake-based port for our own use, but it will split what we build and
what a future user of TileDB from vcpkg will build, and that port is not
without its problems (it failed for example when I tried cross-compiling
to arm64-windows, because it tried to execute the arm64 file.exe on my
x64 machine).

---
TYPE: BUILD
DESC: Update libmagic to version 5.45