if you have: `readonly ref int x = ref y` does this count as a read/write ref now?  or just a read-ref?  It should be the latter.  Can  you check, fix if necessary, and add test?

> if you have: `readonly ref int x = ref y` does this count as a read/write ref now?  or just a read-ref?  It should be the latter.  Can  you check, fix if necessary, and add test?

_Originally posted by @CyrusNajmabadi in https://github.com/dotnet/roslyn/pull/58459#discussion_r774043282_

Follow-up to #58459