chore(profiling): explicitly set or clear NDEBUG for memalloc extension

[nsrip-dd]

The memalloc C extension has debug assert statements. We want them off
by default in case they guard a costly call we wouldn't normally want to
happen. Depending on how the CPython interpreter running setup.py was
built, we may already get -DNDEBUG via the CFLAGS from sysconfig, which
disables asserts. See the setuptools docs.

But rather than rely on that, make sure that asserts
are explicitly disabled for normal builds and explicitly enabled for
debug builds.

Checklist

• PR author has checked that all the criteria below are met
• The PR description includes an overview of the change
• The PR description articulates the motivation for the change
• The change includes tests OR the PR description describes a testing strategy
• The PR description notes risks associated with the change, if any
• Newly-added code is easy to change
• The change follows the library release note guidelines
• The change includes or references documentation updates if necessary
• Backport labels are set (if applicable)

Reviewer Checklist

• Reviewer has checked that all the criteria below are met
• Title is accurate
• All changes are related to the pull request's stated goal
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Newly-added code is easy to change
• Release note makes sense to a user of the library
• If necessary, author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• Backport labels are set in a manner that is consistent with the release branch maintenance policy

[github-actions]

CODEOWNERS have been resolved as:

setup.py                                                                @DataDog/python-guild

[github-actions]

Bootstrap import analysis

Comparison of import times between this PR and base.

Summary

The average import time from this PR is: 232 ± 1 ms.

The average import time from base is: 233 ± 2 ms.

The import time difference between this PR and base is: -1.45 ± 0.07 ms.

Import time breakdown

The following import paths have shrunk:

ddtrace.auto 1.922 ms (0.83%)

ddtrace.bootstrap.sitecustomize 1.254 ms (0.54%)

ddtrace.bootstrap.preload 1.254 ms (0.54%)

ddtrace.internal.products 1.254 ms (0.54%)

ddtrace.internal.remoteconfig.client 0.608 ms (0.26%)

ddtrace 0.667 ms (0.29%)

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-04-16 18:09:36

Comparing candidate commit abd02d8 in PR branch nick.ripley/explicit-ndebug with baseline commit 002e5f9 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 506 metrics, 2 unstable metrics.