perf: avoid heap allocation via local System.Lazy instance

[Flash0ver]

Summary

Avoid a heap allocation via a local System.Lazy instance.

Remarks

In #5159, we introduced a local System.Lazy instance in favor of readability and maintainability. This change is introducing a non-thread-safe struct-based Lazy variant to have your cake and eat it too.

Discussion

Is this new type worth it

I'd argue: yes ... to keep readability of the usage of PreferTransactionNameProvider high, yet avoid 40 B of heap allocations per traced request, which can add up in busy web services

Naming (is hard)

I initially went with LazyLite, to align with ConcurrentBagLite and ConcurrentQueueLite. But arguably, both ConcurrentBagLite and ConcurrentQueueLite are replacements for ConcurrentBag and ConcurrentQueue respectively, where LazyLite does not replace Lazy, but should only be used for local variables when there is no thread contention at all.

Changes

• move existing BatchProcessorBenchmarks to a new Internal namespace
  • the list of documents in the root of Sentry.Benchmarks is getting long
  • to be consistent with how /test/ is also mimicking the respective /src/ namespaces
• a fix to the command in benchmarks/Sentry.Benchmarks/README.md
• added LazyLite + Tests + Benchmarks
• replaced the local Lazy usage with LazyLite
  • added via feat: Add PreferTransactionNameProvider option #5159

---

#skip-changelog

[Flash0ver]

question: exception

If the factory-callback throws, we propagate the Exception, but only once ... I think System.Lazy captures it and re-throws it every time accessing Value. On the other hand, we don't really need this functionality right now.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.22%. Comparing base (afd3873) to head (87f9f46).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5356      +/-   ##
==========================================
+ Coverage   74.19%   74.22%   +0.02%     
==========================================
  Files         508      510       +2     
  Lines       18373    18396      +23     
  Branches     3595     3602       +7     
==========================================
+ Hits        13632    13654      +22     
  Misses       3869     3869              
- Partials      872      873       +1     

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