These methods are slightly more convenient than storing the Bytes
separately. However, it it feels unsanitary to reach in and access this
data directly. Both of the users of these already have the
[Readonly]Bytes available in their constructors, and can easily avoid
using these methods, so let's remove them entirely.
The conversion to AK::Stream makes everything much more straightforward
and understandable now, because we remove the custom reader we had.
Because AK::Stream is more tested, it means that the code should be now
more robust against bugs as well.
The ideal size is the size the user will display the image. Raster
formats should ignore this parameter, but vector formats can use
it to generate a bitmap of the ideal size.
