Add TimerOutputs.to_flamegraph(to) to export a FlameGraph Profile

[NHDaly]

Since TimerOutputs are already nested timings, they map 1:1 to a FlameGraph profile. This simply adds the option to export a FlameGraphs.jl FlameGraph profile object, which can then be displayed via many of the flame-graph compatible display packages: ProfileView, ProfileSVG, etc.

[NHDaly]

This PR is a Draft, because I don't know how you feel (@KristofferC) about adding a dependency on FlameGraphs.jl and LeftChildRightSiblingTrees.jl. They seem to have pulled-in quite a lot of dependencies:

(TimerOutputs) pkg> add FlameGraphs LeftChildRightSiblingTrees
  Resolving package versions...
   Updating `~/.julia/dev/TimerOutputs/Project.toml`
  [08572546] + FlameGraphs v0.2.4
  [1d6d02ad] + LeftChildRightSiblingTrees v0.1.2
   Updating `~/.julia/dev/TimerOutputs/Manifest.toml`
  [1520ce14] + AbstractTrees v0.3.3
  [3da002f7] + ColorTypes v0.10.9
  [5ae59095] + Colors v0.12.4
  [5789e2e9] + FileIO v1.4.3
  [53c48c17] + FixedPointNumbers v0.8.4
  [08572546] + FlameGraphs v0.2.4
  [9b13fd28] + IndirectArrays v0.5.1
  [1d6d02ad] + LeftChildRightSiblingTrees v0.1.2
  [189a3867] + Reexport v0.2.0
  [2a0f44e3] + Base64
  [ade2ca70] + Dates
  [b77e0a4c] + InteractiveUtils
  [76f85450] + LibGit2
  [8f399da3] + Libdl
  [37e2e46d] + LinearAlgebra
  [56ddb016] + Logging
  [d6f4376e] + Markdown
  [44cfe95a] + Pkg
  [9abbd945] + Profile
  [3fa0cd96] + REPL
  [9a3f8284] + Random
  [ea8e919c] + SHA
  [9e88b42a] + Serialization
  [6462fe0b] + Sockets
  [2f01184e] + SparseArrays
  [10745b16] + Statistics
  [cf7118a7] + UUIDs

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Attention: Patch coverage is 0% with 21 lines in your changes missing coverage. Please review.

Project coverage is 87.70%. Comparing base (77d7316) to head (72971a8).
Report is 55 commits behind head on master.

Files with missing lines	Patch %	Lines
src/profile.jl	0.00%	21 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master      #92      +/-   ##
==========================================
- Coverage   92.91%   87.70%   -5.22%     
==========================================
  Files           4        5       +1     
  Lines         353      374      +21     
==========================================
  Hits          328      328              
- Misses         25       46      +21     

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[KristofferC]

This PR is a Draft, because I don't know how you feel (@KristofferC) about adding a dependency on FlameGraphs.jl and LeftChildRightSiblingTrees.jl. They seem to have pulled-in quite a lot of dependencies:

I think it is important that this package is very quick to load, for example, right now:

julia> @time using TimerOutputs
  0.003354 seconds (8.45 k allocations: 769.656 KiB)

but with this PR

julia> @time using TimerOutputs
  0.621417 seconds (1.43 M allocations: 96.632 MiB)

(which amazingly is a 200x increase).

So I think we'll need to find another way. If only we had JuliaLang/Pkg.jl#2005 :P

[IanButterworth]

If only we had JuliaLang/Pkg.jl#2005 :P

If only..

[IanButterworth]

Superseded by #186. Thanks @NHDaly !