feat(r): Allow opt-out of warning for unregistered extension types

[paleolimbot]

Closes #631.

# Using pak::pak("apache/arrow-nanoarrow/r#632")
library(nanoarrow)
array <- as_nanoarrow_array(data.frame(x = 1:5, y = letters[1:5]))
array$children$z <- nanoarrow_extension_array(letters[1:5], "some_extension")

# warns!
tibble::as_tibble(array)
#> Warning in warn_unregistered_extension_type(x): z: Converting unknown extension
#> some_extension{string} as storage type
#> Warning in warn_unregistered_extension_type(storage): z: Converting unknown
#> extension some_extension{string} as storage type
#> # A tibble: 5 × 3
#>       x y     z    
#>   <int> <chr> <chr>
#> 1     1 a     a    
#> 2     2 b     b    
#> 3     3 c     c    
#> 4     4 d     d    
#> 5     5 e     e

# doesn't!
options(nanoarrow.warn_unregistered_extension = FALSE)
tibble::as_tibble(array)
#> # A tibble: 5 × 3
#>       x y     z    
#>   <int> <chr> <chr>
#> 1     1 a     a    
#> 2     2 b     b    
#> 3     3 c     c    
#> 4     4 d     d    
#> 5     5 e     e

^{Created on 2024-09-20 with reprex v2.1.1}

[amoeba]

LGTM.

Did you consider extending the "Converting unknown extension %s as storage type" warning to include instructions for disabling the warning? Considering the report in the original issue, it seems likely that the user who gets the warning may not really know where to go for help or what they should do to hide the warning beyond suppressing warnings for the entire call.

So where the current warning is,

Warning message:
In warn_unregistered_extension_type(storage) :
  z: Converting unknown extension some_extension{string} as storage type

A possible improvement could be:

Warning message:
In warn_unregistered_extension_type(storage) :
  z: Converting unknown extension some_extension{string} as storage type. Disable warning with options(nanoarrow.warn_unregistered_extension = FALSE).

or to make it shorter, "See Details section in ?nanoarrow::convert_array.".