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.

.github/workflows/test.yml

@@ -241,17 +241,9 @@ jobs:
           fi
 
           # Check that all runtime files were installed
-          for file in $(git -C runtime ls-files '*.vim' '*.ps' '*.dict' '*.py' '*.tutor'); do
+          for file in $(git -C runtime ls-files '*.vim' '*.ps' '*.dict' '*.py' '*.tutor' '*.awk' '*.sh' '*.bat'); do
             if ! test -e "$INSTALL_PREFIX/share/nvim/runtime/$file"; then
-              printf "%s%s" 'It appears that %s is not installed.' "$file"
-              exit 1
-            fi
-          done
-
-          # Check that some runtime files are installed and are executables
-          for file in $(git -C runtime ls-files '*.awk' '*.sh' '*.bat'); do
-            if ! test -x "$INSTALL_PREFIX/share/nvim/runtime/$file"; then
-              printf "%s%s" 'It appears that %s is not installed or is not executable.' "$file"
+              printf "It appears that %s is not installed." "$file"
               exit 1
             fi
           done