fix: const generation for not string types (#2333)

[DanielBretzigheimer]

This should fix the bug in #2333, but I had to disable the functionality to generate const for not string types. The problem is that the cases in line 957 in JSONSchemaInput.ts currently expect the cases to be strings. But for const generation they could be every type which causes an error when the names are generated.

I may look into it when I have time, for now, I have added a FIXME comment. If someone would like to address this issue, feel free to fix this.