Compatible for the case if the config class of mod updated

[Jaffe2718]

I use Minecraft 1.21.8 + Fabric for testing, and use my own mod as a test case, the configuration class has changed due to a version update. #110

If you use midnightlib 1.7.5, and load the test mod 2.1.0, then you switch to test mod 2.1.3 and restart the game,
it will throw a NullPointerException.

And if you use midnightlib 1.7.6-rc.1 which I provided, it can be compatible for the case if the config class of mod updated.

[Jaffe2718]

midnightlib-test.zip

[Jaffe2718]

move:

test-fabric --> fabric/src/test

test-neoforge --> neoforge/src/test