refactor(build): make installation of runtime/ more effective

Currently files to install in runtime/ is detected by recursive glob
pattern which has two problems:

- cmake needs to do a of work at config time and
  build/runtime/cmake_install.cmake becomes HUGE (2.5MB, biggest config file)
- we need to explicitly specify each file suffix used in the entire
  runtime, which is duplication of information.

These globs specify every single file in a subdirectory.
Thus, we can just install every runtime/ subdirectory as a single
install command. Furthermore, at the top-level, only .vim and .lua files
need to be installed.

Further possible refactor: we could move files which does not belong
in $PREFIX/runtime out of $REPO/runtime. Then runtime could be installed
with a single install_helper(DIRECTORY ...) command.

cmake/InstallHelpers.cmake

@@ -167,12 +167,3 @@ function(glob_wrapper outvar)
   endif()
   set(${outvar} ${${outvar}} PARENT_SCOPE)
 endfunction()
-
-function(globrecurse_wrapper outvar root)
-  if(${CMAKE_VERSION} VERSION_LESS 3.12)
-    file(GLOB_RECURSE ${outvar} RELATIVE ${root} ${ARGN})
-  else()
-    file(GLOB_RECURSE ${outvar} CONFIGURE_DEPENDS RELATIVE ${root} ${ARGN})
-  endif()
-  set(${outvar} ${${outvar}} PARENT_SCOPE)
-endfunction()