feat(c/driver/postgresql): Support JSON and JSONB types

[paleolimbot]

This PR adds support for JSON and JSONB types. Before this PR, the raw COPY was returned: for JSON, this would have been the bytes of a the JSON string. For JSONB, this would have been the bytes of the JSON string prefixed by 0x01, which is the one and only version number of tthe JSONB COPY binary format.

This PR routes it through the string type. We could also route this through the JSON canonical extension type by adding some metadata. I don't think an implementation of that type exists anywhere yet (but it might functionally be the same since pyarrow/Arrow C++ would just drop the extension metadata).

The testing here is a bit repetitive...we could definitely improve on reducing duplication in the test cases 😬 .

Closes #2068.

Reproducer in R:

library(adbcdrivermanager)
#> Warning: package 'adbcdrivermanager' was built under R version 4.3.3

con <- adbc_database_init(
  adbcpostgresql::adbcpostgresql(), 
  uri = "postgresql://localhost:5432/postgres?user=postgres&password=password"
) |> 
  adbc_connection_init()

lots_of_json_url <- "https://github.com/apache/arrow-experiments/raw/main/data/arrow-commits/arrow-commits.jsonl"
lines <- readLines(lots_of_json_url)

con |> 
  execute_adbc("DROP TABLE IF EXISTS much_json")

data.frame(lines = lines) |> 
  write_adbc(con, "much_json")

con |> 
  read_adbc("select lines::jsonb as lines from much_json") |> 
  tibble::as_tibble()
#> # A tibble: 15,487 × 1
#>    lines                                                                        
#>    <chr>                                                                        
#>  1 "{\"time\": \"2024-03-07T02:00:52\", \"files\": 2, \"merge\": false, \"commi…
#>  2 "{\"time\": \"2024-03-06T21:51:34\", \"files\": 1, \"merge\": false, \"commi…
#>  3 "{\"time\": \"2024-03-06T20:29:15\", \"files\": 1, \"merge\": false, \"commi…
#>  4 "{\"time\": \"2024-03-06T07:46:45\", \"files\": 1, \"merge\": false, \"commi…
#>  5 "{\"time\": \"2024-03-05T16:13:32\", \"files\": 1, \"merge\": false, \"commi…
#>  6 "{\"time\": \"2024-03-05T14:53:13\", \"files\": 20, \"merge\": false, \"comm…
#>  7 "{\"time\": \"2024-03-05T12:31:38\", \"files\": 2, \"merge\": false, \"commi…
#>  8 "{\"time\": \"2024-03-05T08:15:42\", \"files\": 6, \"merge\": false, \"commi…
#>  9 "{\"time\": \"2024-03-05T07:56:25\", \"files\": 2, \"merge\": false, \"commi…
#> 10 "{\"time\": \"2024-03-05T01:04:20\", \"files\": 1, \"merge\": false, \"commi…
#> # ℹ 15,477 more rows

^{Created on 2024-08-11 with reprex v2.1.0}