Add otel spans

[jonjohnsonjr]

Given this and these:

• Add otel spans apko#783
• Add otel spans go-apk#72

We can do nice things like see where melange build latency is being spent across both melange and apko.

We spend a good amount of time in BuildGuest (working on that: chainguard-dev/apko#781):

Loading the image into docker takes longer than I'd expect:

But this will be particularly useful when we hit some pathological case where we have unexpected latency.

[jonjohnsonjr]

Once we merge the go-apk and apko PRs, I'll need to bump melange's dep on them and fix some missing context parameters to make sure we have a full chain of context propagation.