Optimize analyzer with parallel package processing

[oittaa]

• Memory optimization
• Public API compatibility
• Stateless private functions

When Go version requirement is updated to at least 1.25 we can drop golang.org/x/sync/errgroup https://pkg.go.dev/sync@master#WaitGroup.Go

On my machine this is a ~8x speedup against big projects like CockroachDB.

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 85.85859% with 28 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.00%. Comparing base (1216c9b) to head (0352631).
⚠️ Report is 163 commits behind head on master.

Files with missing lines	Patch %	Lines
analyzer.go	85.85%	24 Missing and 4 partials ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1466      +/-   ##
==========================================
+ Coverage   68.49%   69.00%   +0.50%     
==========================================
  Files          75       81       +6     
  Lines        4384     6271    +1887     
==========================================
+ Hits         3003     4327    +1324     
- Misses       1233     1727     +494     
- Partials      148      217      +69     

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