Add a Binary format to store test aggregates

[Swatinem]

This defines a binary file format similar to the various cache formats we use in Symbolicator.

The format contains various aggregations for a configurable number of days.

[codecov]

Codecov Report

Attention: Patch coverage is 97.65298% with 28 lines in your changes missing coverage. Please review.

Project coverage is 94.31%. Comparing base (508185c) to head (57bcd00).
Report is 31 commits behind head on main.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/binary/bindings.rs	90.65%	10 Missing ⚠️
src/binary/format.rs	94.01%	10 Missing ⚠️
src/binary/error.rs	0.00%	6 Missing ⚠️
src/binary/writer.rs	99.43%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #51      +/-   ##
==========================================
+ Coverage   88.68%   94.31%   +5.63%     
==========================================
  Files           5       14       +9     
  Lines         707     1900    +1193     
==========================================
+ Hits          627     1792    +1165     
- Misses         80      108      +28     

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[codecov-notifications]

Codecov Report

Attention: Patch coverage is 97.65298% with 28 lines in your changes missing coverage. Please review.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/binary/bindings.rs	90.65%	10 Missing ⚠️
src/binary/format.rs	94.01%	10 Missing ⚠️
src/binary/error.rs	0.00%	6 Missing ⚠️
src/binary/writer.rs	99.43%	2 Missing ⚠️

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[Swatinem]

I believe this should be feature complete now.
I would appreciate a review, and would be happy to schedule another meeting to walk through the code or through the feedback / questions.

[matt-codecov]

should we do some kind of assert to sanity-check the output

[joseph-sentry]

left 1 comment about the use of unsafe, but at a high level this lgtm

i generally agree that there should be more testing done though

(note so i don't forget)
i think we're going to have to add more features:

• filtering by testsuite name
• filtering by name

[joseph-sentry]

just to make sure i understand: the transmute here is saying "whatever the lifetime of format is now, change it such that it satisfies the lifetime we would need for the compiler to be happy"

also, just because i'm curious, is there an alternative to storing the buffer in the struct alongside a data structure that holds references to it?

[Swatinem]

also, just because i'm curious, is there an alternative to storing the buffer in the struct alongside a data structure that holds references to it?

The alternative would be to use a reference with a lifetime :-)

Though that is not allowed in pyo3 bindings, so we have to use self-contained, and thus self-referential data. Which is currently not possible in safe Rust, and we work around that by using an unsafe transmute to essentially turn the lifetime into 'static, meaning it essentially does not carry any lifetime anymore.