feat(r): Implement string view support in R bindings

[paleolimbot]

This PR adds support for string view and binary view types to the R bindings. As a side effect of this, conversion of character vectors to Arrow types is now simpler (just goes through nanoarrow C's array builder) and supports more types (e.g., the arrow package is no longer required to create large_string, large_binary, or fixed_size_binary).

library(nanoarrow)

long_strings <- rep(strrep(letters, 100), 100)

(array <- as_nanoarrow_array(long_strings, schema = na_string_view()))
#> <nanoarrow_array string_view[2600]>
#>  $ length    : int 2600
#>  $ null_count: int 0
#>  $ offset    : int 0
#>  $ buffers   :List of 11
#>   ..$ :<nanoarrow_buffer validity<bool>[0][0 b]> ``
#>   ..$ :<nanoarrow_buffer unknown<string_view>[2600][41600 b]>`
#>   ..$ :<nanoarrow_buffer data<string>[32700 b]> `aaaaaaaaaaaaaaaaaaaaaaaaaaa...`
#>   ..$ :<nanoarrow_buffer data<string>[32700 b]> `ppppppppppppppppppppppppppp...`
#>   ..$ :<nanoarrow_buffer data<string>[32700 b]> `eeeeeeeeeeeeeeeeeeeeeeeeeee...`
#>   ..$ :<nanoarrow_buffer data<string>[32700 b]> `ttttttttttttttttttttttttttt...`
#>   ..$ :<nanoarrow_buffer data<string>[32700 b]> `iiiiiiiiiiiiiiiiiiiiiiiiiii...`
#>   ..$ :<nanoarrow_buffer data<string>[32700 b]> `xxxxxxxxxxxxxxxxxxxxxxxxxxx...`
#>   ..$ :<nanoarrow_buffer data<string>[32700 b]> `mmmmmmmmmmmmmmmmmmmmmmmmmmm...`
#>   ..$ :<nanoarrow_buffer data<string>[31100 b]> `bbbbbbbbbbbbbbbbbbbbbbbbbbb...`
#>   ..$ :<nanoarrow_buffer data<int64>[8][64 b]> `32700 32700 32700 32700 3270...`
#>  $ dictionary: NULL
#>  $ children  : list()

identical(convert_array(array), long_strings)
#> [1] TRUE

^{Created on 2024-09-27 with reprex v2.1.1}

[amoeba]

LGTM. Left some notes.