Traceback "more" enhancements

### What component of Red (cog, command, API) would you like to see improvements on?

traceback

### Describe the enhancement you're suggesting.

Right now, the default UX feels pretty clunky. The feature I proposed was to stop messages from flooding the chat, and it's certainly doing that, but it's also stopping the user from gracefully seeing all messages at once. I'd propose the following enhancements:

1. Change the default number of pages to 2 at a time instead of 1
2. Add a keyword response `all`
3. Tell the user where they can go to configure the number of pages at a time in the response. The language could be:
```
There are still {} messages remaining. Type `more` to continue, `all` to finish, or `file` to upload all contents as a file. Change pagination volume with `[p]set tracebackpagination`.
```
Of course, replace my fake command with the actual command that changes 2 to the user-set pagination volume.

### Anything else?

I really appreciate that you take the time to implement my UX suggestions, and I feel really bad that this one didn't turn out great in its first implementation. I think with these improvements it'll be a much better experience though.

Start by locating the traceback command's pagination and response-handling entry points. Review how `more` currently limits messages, then verify the default page count, `all` response, configuration guidance, and the user-set pagination volume against the requested behavior.

Written by the indexing model from the issue text.