gh-116738: Make `_codecs` module thread-safe #110969

Job	Run time
Check for source changes	13s
Check if generated files are up to date	5m 12s
Docs	0s
Ubuntu SSL tests with OpenSSL (1.1.1w)	1m 59s
Hypothesis tests on Ubuntu	5m 44s
Ubuntu SSL tests with OpenSSL (3.0.13)	2m 3s
Ubuntu SSL tests with OpenSSL (3.1.5)	1m 55s
Ubuntu SSL tests with OpenSSL (3.2.1)	2m 3s
Address sanitizer	9m 24s
CIFuzz (address)	20m 6s
CIFuzz (undefined)	20m 25s
CIFuzz (memory)	21m 27s
Windows / build and test (x64)	15m 41s
Windows / build (arm64)	2m 40s
Windows / build and test (x86)	15m 13s
macOS / build and test (macos-14)	9m 15s
macOS / build and test (macos-13)	10m 2s
Windows (free-threading) / build and test (x86)	22m 10s
Windows (free-threading) / build and test (x64)	20m 56s
Windows (free-threading) / build (arm64)	2m 36s
macOS (free-threading) / build and test (macos-14)	8m 36s
Ubuntu / build and test	7m 11s
Ubuntu (free-threading) / build and test	9m 52s
WASI / build and test	10m 52s
Thread sanitizer / Thread sanitizer	4m 31s
Thread sanitizer (free-threading) / Thread sanitizer	8m 0s
All required checks pass	9s
	3h 58m 15s

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