fix(prof): use cached heap in alloc_prof_orig_* functions

[realFlowControl]

Description

A crash report ...

0x55af66530fbf _zend_mm_alloc
0x7fe72dea8401 alloc_prof_orig_alloc (/go/src/github.com/DataDog/apm-reliability/dd-trace-php/profiling/src/allocation/allocation_le83.rs:379)
0x7fe72dea82de alloc_prof_malloc (/go/src/github.com/DataDog/apm-reliability/dd-trace-php/profiling/src/allocation/allocation_le83.rs:350)
0x55af6654bcc5 zend_register_constant
0x7fe72dea7635 execute_internal (/go/src/github.com/DataDog/apm-reliability/dd-trace-php/profiling/src/wall_time.rs:79)
0x55af665cd353 zend_execute
0x55af6655d2c8 zend_execute_scripts
0x55af664f79ae php_execute_script
0x7fe732896305 __libc_start_main
0x55af66248c61 _start

... indicated that _zend_mm_alloc was being called with an invalid heap pointer. This invalid pointer originated from the call to zend::zend_mm_get_heap() within alloc_prof_orig_alloc which is weird and can only mean that "something" changed the current heap via zend_mm_set_heap() after we installed our hooks in RINIT to something invalid, but I could not find any other extension that are known for these kind of things in the crash report.

So: In the end it is the right thing to call the heap that we registered with.

Reviewer checklist

• Test coverage seems ok.
• Appropriate labels assigned.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 61.64%. Comparing base (0994638) to head (61be8bf).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3547      +/-   ##
==========================================
- Coverage   61.74%   61.64%   -0.11%     
==========================================
  Files         143      143              
  Lines       13045    13045              
  Branches     1704     1704              
==========================================
- Hits         8055     8041      -14     
- Misses       4228     4241      +13     
- Partials      762      763       +1     

see 3 files with indirect coverage changes

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0994638...61be8bf. Read the comment docs.

🚀 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.

[pr-commenter]

Benchmarks [ profiler ]

Benchmark execution time: 2025-12-23 16:11:10

Comparing candidate commit 61be8bf in PR branch florian/fix-allocs with baseline commit 0994638 in branch master.

Found 0 performance improvements and 4 performance regressions! Performance is the same for 24 metrics, 8 unstable metrics.

scenario:php-profiler-timeline-memory-control

• 🟥 cpu_user_time [+38.401ms; +46.095ms] or [+6.367%; +7.642%]
• 🟥 execution_time [+35.749ms; +43.575ms] or [+5.665%; +6.905%]

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

• 🟥 cpu_user_time [+22.816ms; +85.620ms] or [+2.006%; +7.529%]
• 🟥 execution_time [+24.460ms; +43.177ms] or [+2.619%; +4.623%]