null termination for strings

Strings in the component model are represented as pointers with a length and are allocated into component memory via the cabi_realloc function provided by the component.

When interfacing with APIs that work with "legacy" null-terminated strings, there is a need to perform an additional realloc to add the null termination to the string pointer, which can result in an unnecessary copy.

If, the component model were to explicitly define strings with null terminators for these kinds of legacy API use cases, that would avoid the need for this extra interop work.

It's come up a couple of times for me already now in practical component model workflows. I think it would be useful, but I don't have a very strong opinion on it. I thought it worth discussing as an option.

Start by reviewing the component model's current string representation and the role of cabi_realloc in component memory allocation. Compare the proposed null-termination behavior with the needs of legacy null-terminated APIs, then determine whether the specification change has a sufficiently defined scope and accepted outcome.