Add `record_bytes` to `Visit`

[mattrutherford]

Motivation

We use a lot of data that's encoded as bytes that we would like to record to spans and events. While it's possible to use the debug representation, this is not so efficient.

Solution

Add record_bytes method to the Visit trait which defaults to use record_debug in the same way as the existing methods.

[hawkw]

Since this is a tracing-core change, it would be nice to get @carllerche's approval on this.

[mattrutherford]

Thanks - if the change is acceptable, I can add more documentation / examples.

[dvdplm]

@hawkw this one would be good to get in some day soon. Anything I can do to help expedite the review here?

:)

[carllerche]

I don't have a problem w/ this.

[mattrutherford]

This is still something that's going to be useful - anything I can do to move it along? Or any concerns?

[dvdplm]

Any news on when this might get merged?

[bryangarza]

After a rebase, this could probably be merged