For JSON objects represented as map<ascii, int>, don't treat ASCII keys as a nested JSON string. We were doing that prior to the patch, which led to parsing errors. Included the error offset where JSON parsing failed for rjson::parse related functions to help identify parsing errors better. Fixes: #7949 Signed-off-by: Michael Huang <michaelhly@gmail.com> Closes scylladb/scylladb#15499