arrow

GH-34211: [R] Make sure Arrow arrays are unmaterialized before attempting to access the underlying ChunkedArray (#34489)

### Rationale for this change

When we attempt to re-use an object that Arrow itself created previously by wrapping a chunked array, we will get a crash if this object has been materialized (i.e., R values have been accessed and the ChunkedArray reference deleted). This behaviour changed between 10.0.0 and 11.0.0 because I redid the ALTREP implementation just after the 10.0.0 release.

The following test crashes R on main and 11.0.0 but passes after this PR:

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

test_that("Materialized ALTREP arrays don't cause arrow to crash when attempting to bypass", {
  a_int <- Array$create(c(1L, 2L, 3L))
  b_int <- a_int$as_vector()
  expect_true(is_arrow_altrep(b_int))
  expect_false(test_arrow_altrep_is_materialized(b_int))
  
  # Some operations that use altrep bypass
  expect_equal(infer_type(b_int), int32())
  expect_equal(as_arrow_array(b_int), a_int)
  
  # Still shouldn't have materialized yet
  expect_false(test_arrow_altrep_is_materialized(b_int))
  
  # Force it to materialize and check again
  test_arrow_altrep_force_materialize(b_int)
  expect_true(test_arrow_altrep_is_materialized(b_int))
  expect_equal(infer_type(b_int), int32())
  expect_equal(as_arrow_array(b_int), a_int)
})
#> Test passed 🎉
```

### What changes are included in this PR?

We used a function called `is_arrow_altrep()` to check if we could safely access the ChunkedArray reference; however, *materialized* ALTREP arrays still cause this return `true`. I added a new function `is_unmaterialized_arrow_altrep()` and replaced usage that depended on the ChunkedArray actually existing to use it.

### Are these changes tested?

Yes.

### Are there any user-facing changes?

No.
* Closes: #34211

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