[R] Map/list equality tests are failing only on the sanitizer nightlies

[paleolimbot]

Describe the bug, including details regarding any error messages, version, and platform.

I don't know why this is happening only on the sanitizer nightlies (test-ubuntu-18.04-r-sanitizer and test-fedora-r-clang-sanitizer) , but it seems to be the case.

These tests were added in #14847. @wjones127 any ideas?

Component(s)

R

[paleolimbot]

This is also failing on the valgrind build: https://dev.azure.com/ursacomputing/crossbow/_build/results?buildId=42194&view=logs&j=0da5d1d9-276d-5173-c4c4-9d4d4ed14fdb&t=d9b15392-e4ce-5e4c-0c8c-b69645229181&l=27730

── Failure ('test-parquet.R:460'): Can read parquet with nested lists and maps ──
pq$a$type == list_of(list_of(list_of(utf8()))) is not TRUE

`actual`:   FALSE
`expected`: TRUE 
Backtrace:
    ▆
 1. └─arrow:::expect_equal(pq$a$type, list_of(list_of(list_of(utf8())))) at test-parquet.R:460:2
 2.   └─testthat::expect_true(...) at tests/testthat/helper-expectation.R:36:4
── Failure ('test-parquet.R:463'): Can read parquet with nested lists and maps ──
pq$a$type == map_of(utf8(), map_of(int32(), field("val", boolean(), nullable = FALSE))) is not TRUE

`actual`:   FALSE
`expected`: TRUE 
Backtrace:
    ▆
 1. └─arrow:::expect_equal(...) at test-parquet.R:463:2
 2.   └─testthat::expect_true(...) at tests/testthat/helper-expectation.R:36:4

[wjones127]

This is failing for me locally as well now. expect_equal() is failing, but expect_true(pq$a$type$Equals(<expected type>)) is not.

[jonkeane]

I know what's going on here. I can send a PR unless you've already got it will?