[recastnavigation] Update to 1.6.0 and use official CMakeLists

[JackBoosY]

Related: recastnavigation/recastnavigation#630

[dg0yt]

Given the GH repo and CMake config name, renaming the port to recastnavigation should be seriously considered (and making the legacy port name simply depend on the new name).
In that case, the transitional config (see below) could be limited to the legacy port, and an additional transition warning can be printed when the legacy port is built.

[JackBoosY]

Given the GH repo and CMake config name, renaming the port to recastnavigation should be seriously considered (and making the legacy port name simply depend on the new name).

Maybe not, upstream didn't complain about this.

[dg0yt]

Given the GH repo and CMake config name, renaming the port to recastnavigation should be seriously considered (and making the legacy port name simply depend on the new name).

Maybe not, upstream didn't complain about this.

It is not about upstream. It is about users.
FTR repology has 1 package for recast (vcpkg) and 26 packages for recastnavigation.

[JonLiu1993]

Note: I will be converting your PR to draft status. When you respond, please revert to "ready for review". That way, I can be aware that you've responded since you can't modify the tags.

[JonLiu1993]

Tested usage successfully by recastnavigation:x64-windows:

Total install time: 692 us
recastnavigation provides CMake targets:

    # this is heuristically generated, and may not be correct
    find_package(recastnavigation CONFIG REQUIRED)
    # note: 1 additional targets are not displayed.
    target_link_libraries(main PRIVATE RecastNavigation::Detour RecastNavigation::Recast RecastNavigation::DebugUtils RecastNavigation::DetourCrowd)