I went through all callers of adopt_own() and replaced them with
try_make<>() if possible or adopt_nonnull_own_or_enomem() else
in cases where it was easy (i.e. in functions already returning
ErrorOr).
No intended behavior change.
For now, this is limited to strings that are 3 bytes or less. We can use
7 bytes on 64-bit platforms, but we do not yet assume 64-bit for Lagom
hosts (e.g. wasm).