Remove unused signature features

### Describe the problem

For embedded usages of the generated exi code, it would be nice, if some large unused types of XML signature could be excluded from generated exiDocument structure. Especially those which are mentioned as "shall not be used" in e.g. ISO15118-2 standard:
This would free a lot of currently reserved RAM of the exi structure.

### Describe your solution

Add a list to config like iso2_fragments, where also xmlsig functions can be filtered. Those structures can be generated, but should not be added to exiDocument and xmlsigFragment struct.
If any of those types appear while encode/decode anyway, an error should be thrown.

### Additional context

_No response_