OpenSystemsDevelopment / qpdf

Use QPDF_Stream::writeStreamJSON.
Factor out the json_stream_data == qpdf_sj_file case.

(Replacing the temporary implementation from the last commit.)

writeStreamJSON is a temporary implementation minimally adapted from
getStreamJSON.

Also, test writing JSON v1 files and files with deeply nested containers.

Provide a custom method to check whether a name is valid utf8. Integrate
checking for characters that need to be escaped in JSON.

Create an alternative to getJSON to allow an object handle to be written as JSON without the overhead of creating a JSON object.

Create a simple utility class for writing JSON to a pipeline.

The code accepted values other than /Yes but still used /Yes as the
checked value instead of obeying the normal appearance dictionary.

...as well as some cases generated in CI from earlier attempts at
fixing this.

A parse error in stream data in which stream data contained a nested
object would cause a crash because qpdf was not correctly updating its
internal state. Rework the QPDF json reactor to not be sensitive to
parse errors in this way.

Allow "n:/pdf-syntax" JSON syntax for dictionary keys

Update TODO.md regarding indirect nulls in QPDF_Dictionary

Also, modernize for loop.

Instead of overwriting cur_row.data() use clear and insert.