Reduce allocations in ItemGroupLoggingHelper.GetParameterText

[KirillOsenkov]

See related:
#4907

This is really inefficient and allocates too much.

[KirillOsenkov]

Oops, this could be a dupe of #2200

[KirillOsenkov]

Looks like the Universe wants me to fix this perf issue

[KirillOsenkov]

#5217

[KirillOsenkov]

#5218

[KirillOsenkov]

This is mostly fixed, but I want to repurpose this issue to see if I can get rid of having a StringBuilder in the first place. If we just pass the parameters and items with metadata directly to the loggers (on the TaskStartedEventArgs presumably), then the loggers will not need to allocate the strings altogether, they'll write into their streams directly.

We can have the method that produces these strings on the Args in case the logger still wants the strings.

We'll need to think how to make this change backwards compatible, such that the loggers that are unaware of this change still get the exact same behavior as before.

But certainly I'd like to optimize this throughput for binary logger to minimize the allocation overhead.

[KirillOsenkov]

Fixed by #6155