gh-120496: Make enum_iter thread safe #116643

Job	Run time
Check for source changes	10s
Check if generated files are up to date	5m 0s
Address sanitizer	9m 11s
Ubuntu SSL tests with OpenSSL (1.1.1w)	1m 59s
CIFuzz (address)	19m 35s
Ubuntu SSL tests with OpenSSL (3.0.13)	2m 4s
Hypothesis tests on Ubuntu	5m 46s
CIFuzz (undefined)	20m 30s
Ubuntu SSL tests with OpenSSL (3.1.5)	2m 6s
CIFuzz (memory)	20m 2s
Ubuntu SSL tests with OpenSSL (3.2.1)	1m 58s
Windows / build and test (x64)	17m 32s
Windows / build (arm64)	2m 45s
Windows / build and test (x86)	17m 12s
macOS / build and test (ghcr.io/cirruslabs/macos-runner:sonoma)	4m 46s
macOS / build and test (macos-13)	10m 55s
macOS (free-threading) / build and test (ghcr.io/cirruslabs/macos-runner:sonoma)	5m 16s
Ubuntu / build and test	10m 12s
Ubuntu (free-threading) / build and test	9m 13s
Windows (free-threading) / build and test (x64)	22m 57s
Thread sanitizer / Thread sanitizer	5m 12s
Thread sanitizer (free-threading) / Thread sanitizer	7m 38s
WASI / build and test	10m 52s
Windows (free-threading) / build (arm64)	2m 44s
Windows (free-threading) / build and test (x86)	23m 38s
Docs / Docs	1m 55s
Docs / Docs (Oldest Sphinx)	1m 59s
Docs / Doctest	16m 9s
All required checks pass	3s
	4h 19m 19s

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