feat: Add rbspy as a supported tracer, support post-processing

[dalehamel]

This adds rbspy as a supported tracer, the first non-bpf based tracer, for profiling Ruby processes.

This also adds support for post-processing with tracers, and takes advantage of this to generate both speedscope and flamegraph output for rbspy.

[leodido]

Are we sure do we want non-bpf based tracers?

I believe this needs a bit more discussion between maintainers :)

[dalehamel]

Are we sure do we want non-bpf based tracers? I believe this needs a bit more discussion between maintainers :)

FYI we discussed this on slack, I'll be adding some official docs in another PR with guidance on what generic tracers we should accept, but the current thought is that as long as it doesn't require the target program be significantly modified, and follows these three pillars:

• Does it adhere to either the system or process tracing interfaces we already have (or both)
• Does it have broad appeal / will it be useful to a wide audience
• Does it bloat the size of our trace runner image a lot