Use BoxSize::Auto for most tests.
Use BoxSize::Auto for most tests.

We still need the other variants to test size handling.

There's a trade-off here between the ease of writing tests
and having an extra consistency check on the produced box
data. We might want to go back and fix the sizes later.

kinetiknz/mp4parse-rust,mozilla/mp4parse-rust,kinetiknz/mp4parse-rust