neovim: test-harness code should use the root init.lua

[fidgetingbits]

Now that pokey added a debug/test init.lua at the root folder, I think it probably makes sense that the test harness just uses that rather than maintain its own at packages/test-harness/src/config/init.lua? The only thing I'm not sure is if a sub package like test-harness can actually files from the parent folder or if its confined to its own workspace. I don't plan to look at this for now, so just filing so we don't forget.

Caveat is test setup will use lazy and other plugins that aren't critical too running the test harness.