stackdriver: Add latency metric for write log entries HTTP request. #4506

Job	Run time
pr-windows-build / Determine build info	6s
pr-windows-build / call-build-windows-package (Windows 32bit, x86, C:\vcpkg\packages\openssl_x86-windows-static, x86...	20m 47s
pr-windows-build / call-build-windows-package (Windows 64bit, x64, C:\vcpkg\packages\openssl_x64-windows-static, x64...	19m 22s
pr-windows-build / call-build-windows-package (Windows 64bit (Arm64), amd64_arm64, C:\vcpkg\packages\openssl_arm64-w...	22m 0s
pr-windows-build / Handle upload to S3	13s
run-windows-unit-tests / call-build-windows-unit-test (Windows 32bit, x86, C:\vcpkg\packages\openssl_x86-windows-static, x...	20m 22s
run-windows-unit-tests / call-build-windows-unit-test (Windows 64bit, x64, C:\vcpkg\packages\openssl_x64-windows-static, x...	18m 31s
	1h 41m 21s

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