feat(lua): vim.region accepts getpos() arg (#22635)

test/functional/lua/vim_spec.lua

@@ -2297,6 +2297,10 @@ describe('lua stdlib', function()
       insert([[αα]])
       eq({0,5}, exec_lua[[ return vim.region(0,{0,0},{0,4},'3',true)[0] ]])
     end)
+    it('getpos() input', function()
+      insert('getpos')
+      eq({0,6}, exec_lua[[ return vim.region(0,{0,0},'.','v',true)[0] ]])
+    end)
   end)
 
   describe('vim.on_key', function()