Fix profiling memory limit under a pre-existing hard rlimit

[tautschnig]

The perf-record subprocess set its RLIMIT_AS with a hard limit of -1 (unlimited) in preexec_fn. Raising the hard limit requires privilege, so whenever the calling shell had already imposed a finite hard limit (e.g. an outer ulimit -v), setrlimit raised ValueError inside preexec_fn and the benchmark could not run at all. Set only the soft limit, clamped to the existing hard limit.

• Each commit message has a non-empty body, explaining why the change was made.
• n/a Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• n/a The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
• n/a My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[Copilot]

Pull request overview

This PR fixes the profiling runner’s perf record subprocess setup so it no longer fails when invoked under an existing finite hard RLIMIT_AS (e.g., from an outer ulimit -v). Instead of attempting to raise the hard limit to “unlimited” (which can require privilege and can throw in preexec_fn), it now sets only the soft limit, clamped to the existing hard limit.

Changes:

• Add _limit_address_space(memory_mb) helper to set RLIMIT_AS soft limit while preserving the existing hard limit.
• Replace the inline setrlimit(..., (soft, -1)) lambda with a call to the helper in run_benchmark.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.83%. Comparing base (f71fdad) to head (83d6392).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #9126   +/-   ##
========================================
  Coverage    80.83%   80.83%           
========================================
  Files         1715     1715           
  Lines       189948   189948           
  Branches        73       73           
========================================
  Hits        153540   153540           
  Misses       36408    36408           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.