Grow the json_view dump's output in steps and compare raw-number dumps

- The output string reserves the size estimate (the source extent) and grows
  in steps of 64 KiB within it, instead of being resized to the estimate at
  once: resize() zero-fills, and for a pretty-printed source the estimate is
  far larger than the compact output. citm_catalog dump: 342 -> 283 us on
  x86-64, 144 -> 134 us on Apple M1.
- bench_corpus compares the dump with source numbers with yyjson writing
  numbers read as raw text (YYJSON_READ_NUMBER_AS_RAW); both write the same
  bytes.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

tests/benchmarks/json_view/README.md

@@ -50,7 +50,8 @@ JSON-RPC request (`rpc`):
 | dump | serialize a parsed document (compact) |
 
 `bench_corpus.cpp` runs parse, traverse, and dump on any list of files, so that no library is tuned to a handful of
-documents.
+documents. Its dump also writes the numbers as they are in the input: `json_view` with `number_format::source`, and
+yyjson with numbers read as raw text (`YYJSON_READ_NUMBER_AS_RAW`), without converting them.
 
 `bench_edit.cpp` measures read-modify-write: parse, apply the same logical edits with each library's own API, and
 serialize (compact). Workloads: `patch` (a handful of edits at fixed places) and `update` (edits in every record).