chore(di): guard against mutable module container

[P403n1x87]

When disovering functions on module import, we look at the module as a container of function-like objects. If the module is partially loaded, its __dict__ might mutate. We ensure to iterate over a copy of the module's __dict__ when iterating over it. We expect the original module to mutate dynamically at runtime, so by the time we make a copy of its underlying lookup dict, we are able to detected at the very least everything that corresponds to the actual source code.

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• The change includes tests OR the PR description describes a testing strategy
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• Newly-added code is easy to change
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[github-actions]

CODEOWNERS have been resolved as:

ddtrace/debugging/_function/discovery.py                                @DataDog/debugger-python

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-09-30 14:35:56

Comparing candidate commit 5bec53b in PR branch chore/di-guard-mutable-module-container with baseline commit 7e8eb0b in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 371 metrics, 53 unstable metrics.