Add runner options to enable valgrind subprocess tracking

[GuillaumeLagrange]

Related: CodSpeedHQ/valgrind-codspeed#25

Not to be merged until valgrind-codspeed has been released and required version has been bumped

[greptile-apps]

Greptile Summary

Adds opt-in Valgrind subprocess measurement support.

• Introduces a shared CLI and environment option for subprocess tracking.
• Propagates the option through orchestrator and executor configuration.
• Adjusts Valgrind invocation and output handling for subprocess and thread measurements.
• Removes the exec harness’s previous subprocess rejection.

Confidence Score: 4/5

The PR is not yet safe to merge because enabling subprocess tracking passes an unsupported Valgrind option value and prevents the benchmark from launching.

The subprocess-tracking path still emits --instr-atstart=inherit, while the pinned Valgrind parser treats this as a boolean option accepting only yes or no, so the newly exposed feature fails before benchmark execution.

Files Needing Attention: src/executor/valgrind/measure.rs

Important Files Changed

Filename	Overview
src/cli/shared.rs	Adds the shared opt-in CLI and environment configuration for simulation subprocess tracking.
src/executor/config.rs	Propagates subprocess-tracking configuration from orchestration into each execution.
src/executor/valgrind/measure.rs	Changes Valgrind argument construction to support subprocess and per-thread simulation output.
crates/exec-harness/src/analysis/mod.rs	Removes the post-execution guard that rejected benchmarks spawning Valgrind-traced subprocesses.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart LR
  A["CLI flag / environment variable"] --> B["OrchestratorConfig"]
  B --> C["ExecutorConfig"]
  C --> D["Valgrind argument construction"]
  D --> E["Instrument benchmark subprocesses"]
  E --> F["Combined simulation artifacts"]

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_{Reviews (2): Last reviewed commit: "chore: stop skipping rustup wrapper for ..." | Re-trigger Greptile}

[codspeed-hq]

Merging this PR will not alter performance

✅ 14 untouched benchmarks
⏩ 3 skipped benchmarks¹

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_{Comparing cod-2349-support-subprocesses-in-valgrind (5ce8ad4) with main (8b253c6)}

Footnotes

1. 3 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩