ARROW-10114: [R] Segfault in to_dataframe_parallel with deeply nested structs
ARROW-10114: [R] Segfault in to_dataframe_parallel with deeply nested structs

``` r
library(arrow, warn.conflicts = FALSE)
download.file("https://gist.githubusercontent.com/mskyttner/6700d6a7fe4c3d296f449171897a3ed6/raw/9f65035b3ba6d2859c5fedffced230b6184d4149/head.jsonl", "/tmp/head.jsonl")
df <- read_json_arrow("/tmp/head.jsonl")
names(df)
#> [1] "master"            "publications"      "publication_count"
```

<sup>Created on 2020-10-09 by the [reprex package](https://reprex.tidyverse.org) (v0.3.0.9001)</sup>

Closes #8411 from romainfrancois/ARROW-10114

Authored-by: Romain Francois <b8aabb4b95c817d9df69b6be95b2b94d6b1efe17@rstudio.com>
Signed-off-by: Neal Richardson <beb59f0141269d2d04e73d0dcc1967b64ba87e13@gmail.com>

cpcloud/arrow,icexelloss/arrow,apache/arrow,icexelloss/arrow,kou/arrow,icexelloss/arrow,apache/arrow,cpcloud/arrow,apache/arrow,xhochy/arrow,icexelloss/arrow,kou/arrow,wesm/arrow,xhochy/arrow,cpcloud/arrow,apache/arrow,laurentgo/arrow,icexelloss/arrow,apache/arrow,laurentgo/arrow,laurentgo/arrow,laurentgo/arrow,apache/arrow,apache/arrow,wesm/arrow,xhochy/arrow,kou/arrow,cpcloud/arrow,apache/arrow,kou/arrow,kou/arrow,laurentgo/arrow,kou/arrow,laurentgo/arrow,laurentgo/arrow,xhochy/arrow,wesm/arrow,cpcloud/arrow,xhochy/arrow,icexelloss/arrow,kou/arrow,wesm/arrow,wesm/arrow,xhochy/arrow,wesm/arrow,icexelloss/arrow,cpcloud/arrow,wesm/arrow,xhochy/arrow,wesm/arrow,wesm/arrow,kou/arrow,kou/arrow,kou/arrow,icexelloss/arrow,xhochy/arrow,laurentgo/arrow,laurentgo/arrow,icexelloss/arrow,wesm/arrow,cpcloud/arrow,icexelloss/arrow,cpcloud/arrow,laurentgo/arrow,laurentgo/arrow,laurentgo/arrow,kou/arrow,cpcloud/arrow,icexelloss/arrow,icexelloss/arrow,apache/arrow,xhochy/arrow,cpcloud/arrow,cpcloud/arrow,xhochy/arrow,xhochy/arrow,apache/arrow,wesm/arrow,cpcloud/arrow,apache/arrow,apache/arrow,laurentgo/arrow,apache/arrow,laurentgo/arrow,apache/arrow,xhochy/arrow,laurentgo/arrow,icexelloss/arrow,cpcloud/arrow,wesm/arrow,kou/arrow,wesm/arrow,xhochy/arrow,kou/arrow,icexelloss/arrow,kou/arrow,xhochy/arrow,cpcloud/arrow,wesm/arrow,xhochy/arrow