There are some number of things that are not currently supported for layered tables:

• custom collators
• reserve()

Currently we just silently do the broken logic if we get a call to any of these unsupported API. Instead of doing this we should produce a clear error message if we enter the unsupported part of the code.

We've decided not to produce a failure in case of modify() as a part of this PR since it has an extensive testing on our side and we are still not sure whether there are any issues or whether using it causes issues in different components.