[R] nanoarrow as an interchange class?

nanoarrow looks very promising for converting between classes that use the Arrow format internally.

For such applications, I imagine that if we define a following default S3 method, we can omit the method definition to each class by defining only the conversion from nanoarrow.

```r
as_foo.default <- function(x) {
as_foo.nanoarrow_array_stream(as_nanoarrow_array_stream(x))
}
```

Is this a good idea? (Although of course it may need to be a later version of nanoarrow)