arrow

GH-34897: [R] Ensure that the RStringViewer helper class does not own any Array references (#35812)

This was identified and 99% debugged by @ lgautier on https://github.com/rpy2/rpy2-arrow/issues/11 . Thank you!

I have no idea why this does anything; however, the `RStringViewer` class *was* holding on to an unnecessary Array reference and this seemed to fix the crash for me. Maybe a circular reference? The reprex I was using (provided by @ lgautier) was:

Install fresh deps:

```bash
pip3 install pandas pyarrow rpy2-arrow
R -e 'install.packages("arrow", repos = "https://cloud.r-project.org/")'
```

Run this python script:

```python
import pandas as pd
import pyarrow
from rpy2.robjects.packages import importr
import rpy2.robjects
import rpy2_arrow.arrow as pyra
base = importr('base')
nanoarrow = importr('nanoarrow')

code = """
    function(df) {
        # df$col1  # no segfault on exit
        # I(df$col1)  # no segfault on exit
        # df$col2  # no segfault on exit
        I(df$col2)  # segfault on exit
    }
"""
rfunction = rpy2.robjects.r(code)

pd_df = pd.DataFrame({
    "col1": range(10),
    "col2":["a" for num in range(10)]
})
pd_tbl = pyarrow.Table.from_pandas(pd_df)
r_tbl = pyra.pyarrow_table_to_r_table(pd_tbl)
r_df = base.as_data_frame(nanoarrow.as_nanoarrow_array_stream(r_tbl))

output = rfunction(r_df)
print(output)
```

Before this PR (installing R/arrow from main) I get:

```
(.venv) dewey@ Deweys-Mac-mini 2023-05-29_rpy % python reprex-arrow.py
 [1] "a" "a" "a" "a" "a" "a" "a" "a" "a" "a"

zsh: segmentation fault  python reprex-arrow.py
```

After this PR I get:

```
(.venv) dewey@ Deweys-Mac-mini 2023-05-29_rpy % python reprex-arrow.py
 [1] "a" "a" "a" "a" "a" "a" "a" "a" "a" "a"
```

(with no segfault)

I wonder if this also will help with #35391 since it's also a segfault involving the Python <-> R bridge.
* Closes: #34897

Authored-by: Dewey Dunnington <dewey@voltrondata.com>
Signed-off-by: Dewey Dunnington <dewey@fishandwhistle.net>