Restructure: Remove R package about arrow-extendr HOT 9 CLOSED

array <- nanoarrow::nanoarow_allocate_array()
schema <- nanoarrow::nanoarrow_allocate_schema()
nanoarrow::nanoarrow_pointer_move(<address of the FFI struct as a string>, array)
nanoarrow::nanoarrow_pointer_move(<address of the FFI struct as a string>, schema)
nanoarrow::nanoarrow_array_set_schema(array, schema)

library(nanoarrow)
library(arrowextendr)

test_f64() |> 
  as_nanoarrow_array()
#> <nanoarrow_array double[3]>
#>  $ length    : int 3
#>  $ null_count: int 1
#>  $ offset    : int 0
#>  $ buffers   :List of 2
#>   ..$ :<nanoarrow_buffer validity<bool>[8][1 b]> `TRUE FALSE TRUE FALSE FALS...`
#>   ..$ :<nanoarrow_buffer data<double>[3][24 b]> `1 0 3`
#>  $ dictionary: NULL
#>  $ children  : list()

test_schema() |> 
  as_nanoarrow_schema()
#> <nanoarrow_schema struct>
#>  $ format    : chr "+s"
#>  $ name      : chr ""
#>  $ metadata  : list()
#>  $ flags     : int 0
#>  $ children  :List of 3
#>   ..$ a:<nanoarrow_schema date64>
#>   .. ..$ format    : chr "tdm"
#>   .. ..$ name      : chr "a"
#>   .. ..$ metadata  : list()
#>   .. ..$ flags     : int 0
#>   .. ..$ children  : list()
#>   .. ..$ dictionary: NULL
#>   ..$ a:<nanoarrow_schema int64>
#>   .. ..$ format    : chr "l"
#>   .. ..$ name      : chr "a"
#>   .. ..$ metadata  : list()
#>   .. ..$ flags     : int 2
#>   .. ..$ children  : list()
#>   .. ..$ dictionary: NULL
#>   ..$ b:<nanoarrow_schema bool>
#>   .. ..$ format    : chr "b"
#>   .. ..$ name      : chr "b"
#>   .. ..$ metadata  : list()
#>   .. ..$ flags     : int 0
#>   .. ..$ children  : list()
#>   .. ..$ dictionary: NULL
#>  $ dictionary: NULL

test_field() |> 
  as_nanoarrow_schema()
#> <nanoarrow_schema binary>
#>  $ format    : chr "z"
#>  $ name      : chr "field_name"
#>  $ metadata  : list()
#>  $ flags     : int 2
#>  $ children  : list()
#>  $ dictionary: NULL

test_datatype() |> 
  as_nanoarrow_schema()
#> <nanoarrow_schema timestamp('s', '')>
#>  $ format    : chr "tss:"
#>  $ name      : chr ""
#>  $ metadata  : list()
#>  $ flags     : int 2
#>  $ children  : list()
#>  $ dictionary: NULL

test_record_batch() |> 
  as_nanoarrow_array_stream()
#> <nanoarrow_array_stream struct<id: int32>>
#>  $ get_schema:function ()  
#>  $ get_next  :function (schema = x$get_schema(), validate = TRUE)  
#>  $ release   :function ()