Add support for Profiles

[BYK]

We have rich profile data and it would be great to enrich the tracing view with this data since we get it from most of the popular SDKs now.

I want to do 2 things with profiles:

• Fill in missing instrumentation data in transactions or at least provide more details under some spans. I think this is easier (at least it is what I'm told) and would immediately bring value.
• Actually have the flamegraph etc for deeper debugging. I was referred to this component which we can easily port: getsentry/sentry@master/static/app/components/profiling/flamegraph/flamegraphPreview.tsx

Resources:

• Profile data format we need to consume: https://develop.sentry.dev/sdk/telemetry/profiles/sample-format-v1/
• Actual profile data from my sample Django app: https://gist.github.com/BYK/2bf873615ddf1bf1ce52efccab1dd347

[BYK]

Some progress on this:

Things to improve:

• We need a way to group/collapse deep spans with just a single child or repeated spans
• We need a way to find at which depth to start showing the "augmented" profile information when we are filling in the gaps for the existing tracing instrumentation. The challenge here is, the span information we collect has no information regarding the dept of the callstack or any stack-related information at all. They mostly correspond to wrapped function calls though so we should be able to run some heuristics there
• Performance itself needs to be worked on. Right now I do all the calculations on the fly at display time. We can (and should) pre-load most of this work at profile ingestion if not all of that.
• We need a toggle for "only show in-app stack frames"

Aside, we can now surface "the most time consuming function calls" under insights with a different processing of the profile data.