build,meson: Make feature options boolean

Different options are set as `feature`, also every possible plugin,
but this may cause confusion.

All options set as `feature` but plugins have been made `boolean` to
avoid further confusions.

`help2man` is also installed in the CI image because is required to
build different libraries.

cli/meson.build

@@ -26,10 +26,11 @@ sources = files(
   'mmcli-sms.c',
 )
 
-deps = [
-  gudev_dep,
-  libmm_glib_dep,
-]
+deps = [libmm_glib_dep]
+
+if enable_udev
+  deps += gudev_dep
+endif
 
 executable(
   'mmcli',