A method stores caller data, awaits I/O, then reads the data. Which parameter best expres…

A method stores caller data, awaits I/O, then reads the data. Which parameter best expresses that contract?

1. `ReadOnlyMemory<byte>` with a documented retention period
2. `ReadOnlySpan<byte>` kept in a class field
3. `Span<byte>` captured by the async continuation
4. `byte*` because pointers provide automatic ownership