Correctly reference utils module

[joshua-holmes]

Hi! I noticed that the utils module (the utils/utils.lua file) was being read as nil. Lua seems to do this weird thing of silently exiting when calling .something on a nil value, so the DAP setup was not working correctly.

This change fixes this issue by importing the utils module like so and adjusting the references to match:

local rt_utils = require('rust-tools.utils.utils')
...
rt_utils.compare(...)

See the photo for evidence that a nil value was being read. On the left is the code I added to log the issue, on the bottom right is the log's output.