Integrate Pyroscope Diff into CI/CD Pipelines

In #373 we introduced this concept for us to compare Pyroscope `main` branch vs `pr-XXX`.

It results in a [comment from "pyroscopebot"](https://github.com/pyroscope-io/pyroscope/pull/373#issuecomment-917192985) that looks like this:

For this particular use case we run a series of generic benchmarks that we created for testing the Pyroscope server. However, we have also heard from some who use Pyroscope to profile their test suite or something similar.

i.e. : `pyroscope exec rspec`

For this we'd like to add the ability for them to integrate with github and have a Flamegraph Diff that compares two different profiles. This may be easiest after we've implemented adhoc profiling in #228 .