arrow

ARROW-18043: [R] Properly instantiate empty arrays of extension types in Table__from_schema (#14519)

This PR supports the following:

``` r
library(arrow, warn.conflicts = FALSE)
#> Some features are not enabled in this build of Arrow. Run `arrow_info()` for more information.

schema_with_ext_type <- schema(
  x = int32(),
  y = vctrs_extension_type(integer())
)

as_arrow_table(schema_with_ext_type)
#> Table
#> 0 rows x 2 columns
#> $x <int32>
#> $y <integer(0)>
```

<sup>Created on 2022-10-26 with [reprex v2.0.2](https://reprex.tidyverse.org)</sup>

It's a little bit cheating, though, because the previous approach is more true to what `ChunkedArray::MakeEmpty()` does. Is there a downside here to creating a `ChunkedArray` with zero chunks (as opposed to a `ChunkedArray()` with one empty chunk)? If there is we can probably work around it via creating an empty array of the storage type and wrapping it.

Authored-by: Dewey Dunnington <dewey@voltrondata.com>
Signed-off-by: Nic Crane <thisisnic@gmail.com>