Improve DebugPrinter

[rukai]

There are two benefits here:

• users of the DebugPrinter transform are given a much higher level message log.
• developers get access to much more succinct debug logs with tracing::error!("look at this {}", message.to_high_level_string()). In particular I was overwhelmed by all the log noise when investigating the failure on CassandraSinkCluster: topology task now processes events #812

In order to allow parsing the message I couldnt implement Display for Message due to needing mutable access, so instead I added a to_high_level_string method.

While writing the format I wanted to prioritize both terseness and including every underlying field in some way.
To do this I was willing to introduce ambiguity in many places, but that is ok because its a format for humans to read not computers.
Some instances where this came up is:

• Options display nothing when None
• Vecs display nothing when empty
• cql query is unparsed text instead of AST
• some fields arent labelled when the meaning should be obvious (assuming you are already familiar with the field)

The result metadata types formatting are not great right now but I want to refactor the underlying types there sometime so not too fussed about that atm.

Many message types are just stubbed to give the standard "{:?}" debug output, I expect we will want to come back and implement those properly later on.

Here is some before and afters:

system.local query/response before:

system.local query/response after:

And a bonus one, that demonstrates multi-row results that I couldnt find a before screenshot for:

[conorbros]

Just a thought as I'd be pretty happy to go ahead with this as is because it's very useful:

Could we do a parameter called expand_long_lists: bool or similar? If false then large lists like the tokens would be truncated to only a couple of elements seeing as it's unlikely you'd want to inspect the entire token list very often.

[rukai]

It sounds useful for debugging, however:

• I dont think we would want to expose it in DebugPrinter
• trying to come up with an API that is flexible while keeping the implementation and API simple is going to be challenging.
• it takes some foresight to know the cases where we truly only want to see part of the message.
  I can imagine it would be annoying to be reading through a debug log and suddenly finding that we need to rerun the test without the truncation because we guessed wrong.

Possibly the way to do it would be to have a configurable line length limit and truncate any lines that go over that limit.

I would like to later on change Varchar("blah") to format as just "blah", that should reduce the result noise without resorting to truncation.
Although I am a little apprehensive about that approach due to the NO_METADATA flag option.

Even with that all said, I wouldnt object if you made a follow up PR to introduce such functionality.