build(profiling): remove once_cell as a dependency

[morrisonlevi]

Description

Replaces once_cell types with ones in the std library (since 1.70). In one case it removes a Lazy instead and handles the non-const parts by writing them in get_module. Note that OnceCell in the stdlib isn't Sync so once_cell::sync::OnceCell was replaced by std::sync::OnceLock in most cases.

My real motivation is to use PHP globals for some things instead of Rust TLS variables. They have been problematic in the memory allocation profiler because of ext/grpc doing unsafe (and wrong, not just unsafe) things. While exploring that, I noticed this cleanup was possible. It's only net new lines of code because there are new comments.

Reviewer checklist

• Test coverage seems ok.
• Appropriate labels assigned.

[datadog-official]

⚠️ Tests

✨ Fix all issues with Cursor

⚠️ Warnings

🧪 27 Tests failed

testSearchPhpBinaries from integration.DDTrace\Tests\Integration\PHPInstallerTest (Datadog) (Fix with Cursor)

DDTrace\Tests\Integration\PHPInstallerTest::testSearchPhpBinaries
Test code or tested code printed unexpected output: Searching for available php binaries, this operation might take a while.

phpvfscomposer://tests/vendor/phpunit/phpunit/phpunit:106

    testSimplePushAndProcess from laravel-58-test.DDTrace\Tests\Integrations\Laravel\V5_8\QueueTest (Fix with Cursor)

testSimplePushAndProcess from laravel-8x-test.DDTrace\Tests\Integrations\Laravel\V8_x\QueueTest (Datadog) (Fix with Cursor)

DDTrace\Tests\Integrations\Laravel\V8_x\QueueTest::testSimplePushAndProcess
Test code or tested code printed unexpected output: spanLinksTraceId: 697b89c200000000fd1d921b94e892c3
tid: 697b89c200000000
hexProcessTraceId: fd1d921b94e892c3
hexProcessSpanId: b75f2dc7a9cb26a4
processTraceId: 18238894713080419011
processSpanId: 13213330167298729636

View all

ℹ️ Info

❄️ No new flaky tests detected

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 8198125 | Docs | Datadog PR Page | Was this helpful? Give us feedback!}

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 62.20%. Comparing base (21d2f00) to head (8198125).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3607      +/-   ##
==========================================
- Coverage   62.24%   62.20%   -0.05%     
==========================================
  Files         141      141              
  Lines       13387    13387              
  Branches     1753     1753              
==========================================
- Hits         8333     8327       -6     
- Misses       4257     4263       +6     
  Partials      797      797              

see 2 files with indirect coverage changes

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[pr-commenter]

Benchmarks [ profiler ]

Benchmark execution time: 2026-01-29 16:27:42

Comparing candidate commit 8198125 in PR branch levi/const-module-entry with baseline commit 21d2f00 in branch master.

Found 0 performance improvements and 2 performance regressions! Performance is the same for 27 metrics, 7 unstable metrics.

scenario:php-profiler-timeline-memory-with-profiler-and-timeline

• 🟥 cpu_user_time [+42.459ms; +90.538ms] or [+2.750%; +5.864%]
• 🟥 execution_time [+49.321ms; +59.317ms] or [+4.045%; +4.864%]