Refactor measurement/profiling chapter

[hsyl20]

I'd like to suggest refactoring the Measurement / Profiling chapter.

I've written some introduction text: #95

Then I think we should present it from the bottom-up:

• binary profiling: perf, cachegrind, etc. Tools that are language agnostic. Limitations due to Haskell execution model
• multi-thread level: OS vs Haskell threads. ThreadScope, etc.
• Cmm level: if we have Cmm specific probes?
• Stg level + rts stats: G-machine level probes: ticky, late cost centers, etc. RTS stats: GC, applications, etc. The bulk of what makes Haskell different to profile than most other languages
• Core level: non-late cost centers, etc.
• Haskell level: user probes (event log), haskell level checks (weigh, nothunks...)

What do you think?

[doyougnu]

I think this is a great idea. Then at the beginning of the book we can have a triage chapter that is observe this symptom --> check this chapter to guide readers to the right place.