gh-123963: Expose GetCurrentByteCount from expat #125038

Job	Run time
Change detection / Compute changed files	13s
Check if generated files are up to date	5m 3s
Windows MSI${{ '' }}	0s
Address sanitizer	7m 37s
Ubuntu SSL tests with OpenSSL (3.0.15)	2m 4s
CIFuzz (address)	19m 55s
Ubuntu SSL tests with OpenSSL (3.1.7)	2m 4s
Hypothesis tests on Ubuntu	5m 23s
CIFuzz (undefined)	20m 49s
Ubuntu SSL tests with OpenSSL (3.2.3)	2m 36s
CIFuzz (memory)	20m 30s
Ubuntu SSL tests with OpenSSL (3.3.2)	2m 9s
Thread sanitizer / Thread sanitizer	4m 47s
Thread sanitizer (free-threading) / Thread sanitizer	7m 3s
WASI / build and test	6m 8s
macOS (free-threading) / build and test (ghcr.io/cirruslabs/macos-runner:sonoma)	5m 20s
macOS / build and test (ghcr.io/cirruslabs/macos-runner:sonoma)	5m 8s
macOS / build and test (macos-13)	17m 41s
Ubuntu / build and test	7m 13s
Ubuntu (free-threading) / build and test	9m 34s
Windows / build (arm64)	2m 58s
Windows (free-threading) / build (arm64)	2m 58s
Windows / build and test (Win32)	15m 12s
Windows (free-threading) / build and test (Win32)	22m 43s
Windows / build and test (x64)	16m 40s
Windows (free-threading) / build and test (x64)	23m 5s
Docs / Docs	1m 50s
Docs / Docs (Oldest Sphinx)	1m 59s
Docs / Doctest	18m 19s
All required checks pass	2s
	4h 17m 3s

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