[Config] Created and switched to new FileNotFoundException

The ```InvalidArgumentException``` is technically wrong. Because the argument itself doesn' t has to be invalid. The file couldn' t be found on the system. I think this is a little better to throw the new ```FileNotFoundException```.

The new Exception class is extending ```InvalidArgumentException``` this way it doesn' t break BC. I haven' t modified the tests at all, this should proof this.

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes (kinda... a little maybe)
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | none
| License       | MIT
| Doc PR        | none (The exception "throwing" isn' t mentioned in the docs.)