I'm a little confused.
Rather than a package manager, CMake is a build system, but people have
written several[1] package[2] managers[3] in CMake (the language), let
alone the other package managers for C/C++, all of which make me
question if anyone ever asked for any of them. I don't think those can
all be brought under one hat (even if limiting ourselves to just the
CMake ones).
OTOH I also think that a CMake importer might not be needed. Contrary
to what advocates of language package managers might tell you,
packaging is actually easier without them (since the developer first of
all has to think about how to reasonably package their stuff for *their
own machine* without anything going "lol, let's just download the whole
Internet during build").
[1] https://github.com/cpp-pm/hunter
[2] https://github.com/cpm-cmake/CPM.cmake
[3]
https://gracicot.github.io/cmake/2020/04/09/i-made-a-package-manager-using-cmake.html
