[libigl] v2.4.0 broken due to port and upstream problems

[FabienPean]

There are numerous issues with the newer version 2.4.0 merged in #26942, most introduced by upstream regressions. While it seemingly "compiles", v2.4.0 is botched. Upstream has been notified libigl/libigl#2186

To Reproduce

Steps to reproduce the behavior:

./vcpkg install libigl

A. Library when using vcpkg with static linkage

Detailed here #30617

B. CMake config files are broken

1. Naming inconsistent
   
2. Main config file not including target file, i.e., missing include(${CMAKE_CURRENT_LIST_DIR}/LibiglConfigTargets.cmake)
3. It means the include folder of igl cannot be found on a simple test case, because it cannot find the target, making the port basically useless.

C. Features have no effects

Upstream repository does not install the targets containing the options, only the core target, see https://github.com/search?q=repo%3Alibigl%2Flibigl%20igl_install&type=code. Moreover, installing does not include copyleft targets https://github.com/libigl/libigl/blob/a05865e2650f22057fcdc0b77c40d2458922f5d8/CMakeLists.txt#L150. So libigl[cgal] has no effects.

[FrankXie05]

Fixed by PR #30617