The Bug:
1. Construct `byte_slice.portion_` with `epee::span(buffer)` which copies a pointer to the SSO buffer to `byte_slice.portion_`
2. It constructs `byte_slice.storage_` with `std::move(buffer)` (normally this swap pointers, but SSO means a memcpy and clear on the original SSO buffer)
3. `slice.data()` returns a pointer from `slice.portion_` that points to the original SSO cleared buffer, `slice.storage_` has the actual string.
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