update config related to folding

1. For python and lua, rely on LSP for folding
2. show fold signs on the right of the number column

lua/plugin_specs.lua

@@ -194,9 +194,9 @@ local plugin_specs = {
       require("statuscol").setup {
         relculright = true,
         segments = {
-          { text = { builtin.foldfunc }, click = "v:lua.ScFa" },
           { text = { "%s" }, click = "v:lua.ScSa" },
           { text = { builtin.lnumfunc, " " }, click = "v:lua.ScLa" },
+          { text = { builtin.foldfunc, " " }, condition = {true, builtin.not_empty}, click = "v:lua.ScFa" },
         },
       }
     end,