arrow

ARROW-14051 [R] Handle conditionals enclosing aggregate expressions

This PR more correctly passes on type information for the temporary columns that are created when nested expressions exist. This isn't needed often, but occasionally the expression type is checked for the purposes of erroring or warning. The two examples where this happens are `ifelse()` and `case_when()`, which resulted in the following (valid) code pulling data into R with a confusing message:

``` r
library(arrow, warn.conflicts = FALSE)
library(dplyr, warn.conflicts = FALSE)

# motvating example
RecordBatch$create(x = c(0, 1, 1), y = c(2, 3, 5), z = c(8, 13, 21)) %>%
  group_by(x) %>%
  summarise(r = ifelse(n() > 1, mean(y), mean(z))) %>%
  collect()
#> Warning: Error : Expression ifelse(..temp0 > 1, ..temp1, ..temp2) not supported
#> in Arrow; pulling data into R
#> # A tibble: 2 × 2
#>       x     r
#>   <dbl> <dbl>
#> 1     0     8
#> 2     1     4
```

After this PR, the above works without warning:

``` r
library(arrow, warn.conflicts = FALSE)
library(dplyr, warn.conflicts = FALSE)

# motvating example
RecordBatch$create(x = c(0, 1, 1), y = c(2, 3, 5), z = c(8, 13, 21)) %>%
  group_by(x) %>%
  summarise(r = ifelse(n() > 1, mean(y), mean(z))) %>%
  collect()
#> # A tibble: 2 × 2
#>       x     r
#>   <dbl> <dbl>
#> 1     0     8
#> 2     1     4
```

I imagine I'm missing some of the complexity here...feel free to let me know!

Closes #11612 from paleolimbot/r-summarise-ifelse

Authored-by: Dewey Dunnington <dewey@fishandwhistle.net>
Signed-off-by: Jonathan Keane <jkeane@gmail.com>