test: keep OOM tests compatible with newer compilers

[yangzhg]

Summary

• Avoid constant huge allocation sizes in OOM stack tests so GCC does not fail the test binary with -Walloc-size-larger-than before the test can exercise runtime OOM behavior.
• Add headroom before padded lazy-parse test buffers and pass the shifted data pointer to avoid GCC 12/13 AVX2 inline -Warray-bounds diagnostics.
• Mark DNode::MetaNode destruction as noinline to avoid GCC 12 incorrectly folding the object-size analysis through DOM teardown.

Why

This is a small compatibility prerequisite before the OOM split PRs. The current master fails locally under GCC 12/13 when compiling :unittest with warning-as-error, even before the oom-core changes can be validated.

Validation

• bazel test :unittest --//:sonic_arch=haswell --//:sonic_dispatch=static --//:sonic_sanitizer=no --test_filter='*Allocator*:*WriteBuffer*' with GCC 13
• CC=gcc-12 CXX=g++-12 bazel test :unittest --//:sonic_arch=haswell --//:sonic_dispatch=static --//:sonic_sanitizer=no --test_filter='*Allocator*:*WriteBuffer*'
• CC=clang CXX=clang++ bazel test :unittest --//:sonic_arch=haswell --//:sonic_dispatch=static --//:sonic_sanitizer=no --test_filter='*Allocator*:*WriteBuffer*'
• git diff --cached --check

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.67%. Comparing base (92964a8) to head (213be6a).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #138   +/-   ##
=======================================
  Coverage   69.67%   69.67%           
=======================================
  Files          27       27           
  Lines        3706     3706           
  Branches     1189     1189           
=======================================
  Hits         2582     2582           
  Misses        211      211           
  Partials      913      913           

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[Copilot]

Pull request overview

This PR updates a few OOM-focused unit tests and a DOM teardown path to avoid GCC 12/13 warning diagnostics (treated as errors) that prevent the tests from building, while preserving the intent of exercising runtime OOM behavior.

Changes:

• Add headroom before padded buffers used by ParseLazy OOM tests and pass the shifted data pointer to avoid GCC -Warray-bounds diagnostics.
• Make the “huge allocation” size in stack OOM tests a runtime value to avoid GCC -Walloc-size-larger-than at compile time.
• Mark DNode::MetaNode’s destructor as noinline to avoid GCC object-size analysis folding through DOM teardown.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
tests/parser_oom_test.cpp	Adds headroom + helper accessor so lazy-parse OOM tests use a shifted buffer pointer and avoid GCC bounds warnings.
tests/allocator_test.cpp	Makes the huge allocation size runtime-derived to keep OOM stack tests buildable under GCC warning-as-error.
include/sonic/dom/dynamicnode.h	Applies noinline to MetaNode destructor to prevent GCC mis-analysis during teardown.

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