Make profile-conversion snapshots more compact and meaningful

[mstange]

Main | Deploy preview

profile-conversion.test.ts was creating a snapshot file that was just a bunch of raw profile JSONs, with around 900 000 lines total.

There's no way to catch regressions with such a test. Whenever we change the shape of the tables in the profile format, it affects so many lines that github's diff viewer will not render the diff, and you wouldn't be able to meaningfully read it anyway.

For example, when I introduced the shared tables, I regressed the dhat importer (it was overwriting some tables with empty tables), and I missed the regression even though the test in theory "caught" it.

This commit replaces the raw profile snapshots with profile "summary" snapshots. See the new snapshot file for examples. I think the new snapshots are definitely more readable / reviewable, but there's also quite a bit of new code to generate them. I'd be happy to cut back on the amount of detail we collect when we make these summaries, to simplify that new code.
(Or maybe we can find a way to share some code with profiler-cli? Not sure.)

The new snapshot file is around 500 lines, and around 160 times smaller than the old snapshot file.

As a second measure of defense, this commit also adds a generic profile consistency checker function called assertProfileIntegrity. This would have caught the dhat regression by itself, because nativeAllocations.stack[0] = 55 would have tripped over the stack table being empty.

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 21 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.51%. Comparing base (b2c0eba) to head (fd7d04a).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/test/fixtures/profile-summary.ts	85.71%	21 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #6152    +/-   ##
========================================
  Coverage   83.50%   83.51%            
========================================
  Files         342      343     +1     
  Lines       36522    36669   +147     
  Branches    10224    10263    +39     
========================================
+ Hits        30497    30623   +126     
- Misses       5597     5618    +21     
  Partials      428      428            

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