Add Rust language coloring

[zthompson47]

This PR is part of an effort to provide more coloring options for cargo-flamegraph in flamegraph-rs/flamegraph#19.

It looks for Rust functions in the stack (i.e. contains "::"), and applies separate color palettes for Rust system functions and user functions.

[codecov]

Codecov Report

Merging #211 (484f718) into master (534eb03) will increase coverage by 0.14%.
The diff coverage is 97.56%.

@@            Coverage Diff             @@
##           master     #211      +/-   ##
==========================================
+ Coverage   89.48%   89.63%   +0.14%     
==========================================
  Files          17       17              
  Lines        2312     2353      +41     
==========================================
+ Hits         2069     2109      +40     
- Misses        243      244       +1     

Impacted Files	Coverage Δ
src/flamegraph/color/mod.rs	83.43% <50.00%> (-0.44%)	⬇️
src/flamegraph/color/palettes.rs	99.39% <100.00%> (+0.08%)	⬆️

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[jonhoo]

This is a great addition, thank you! I left some notes inline.

[zthompson47]

Thanks for the review and your time! I can start another revision tomorrow morning or so, and I left some responses up above.

[zthompson47]

I pushed another commit. I hope that's the right way to go at this point, but I thought it would be most useful to have my latest code up here for review. I'm still kind of new to the collaboration end of this process so I'm hoping I didn't confuse things by introducing new changes at this stage.

[jonhoo]

Not at all — the right way to go is to continuously improve the PR incrementally until we get to it being ready to land :)

[jonhoo]

This looks great, now we just need to get the tests to pass!

[zthompson47]

Excellent! I just tried to merge with upstream/master, and it looks like there are still errors in the tests.

Ok, just realized that my test was failing and fixed it.

FWIW, there were some already-broken tests on my system before this feature which I attributed to not have the right profiling software installed on my end.

[jonhoo]

Looks great, thanks!

[jonhoo]

Released in 0.10.5 🎉

[zthompson47]

Thanks so much for your help on this!

[jonhoo]

Thanks for sticking with it!