h3i: Improve ConnectionSummary stream_map serialization #5885

Job	Run time
quiche_macos (macos-13)	3m 49s
quiche_windows (x86_64-pc-windows-msvc)	4m 38s
quiche_multiarch (aarch64-unknown-linux-gnu)	3m 16s
quiche_windows (i686-pc-windows-msvc)	3m 44s
quiche	4m 3s
quiche_multiarch (armv7-unknown-linux-gnueabihf)	3m 28s
quiche (boringssl-boring-crate)	3m 0s
quiche_multiarch (i686-unknown-linux-gnu)	1m 50s
quiche_windows (x86_64-pc-windows-gnu)	6m 35s
quiche (openssl)	6m 13s
quiche_windows (i686-pc-windows-gnu)	5m 8s
quiche_macos (macos-latest)	1m 45s
android_ndk_lts (aarch64-linux-android)	53s
http3_test	44s
android_ndk_lts (armv7-linux-androideabi)	1m 17s
docker	1m 52s
quiche_ios (x86_64-apple-ios)	1m 7s
android_ndk_lts (x86_64-linux-android)	1m 0s
quiche_ios (aarch64-apple-ios)	1m 7s
android_ndk_lts (i686-linux-android)	53s
	56m 22s

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