h3i: Improve ConnectionSummary stream_map serialization #5890

Job	Run time
quiche_macos (macos-13)	4m 17s
quiche_windows (x86_64-pc-windows-msvc)	3m 46s
quiche_macos (macos-latest)	1m 48s
quiche_windows (i686-pc-windows-msvc)	4m 20s
quiche_windows (x86_64-pc-windows-gnu)	6m 9s
quiche_windows (i686-pc-windows-gnu)	5m 15s
http3_test	48s
docker	1m 49s
android_ndk_lts (aarch64-linux-android)	54s
quiche	3m 46s
android_ndk_lts (armv7-linux-androideabi)	46s
quiche_ios (x86_64-apple-ios)	1m 13s
quiche (boringssl-boring-crate)	2m 56s
android_ndk_lts (x86_64-linux-android)	1m 1s
quiche_multiarch (aarch64-unknown-linux-gnu)	3m 9s
quiche (openssl)	6m 20s
android_ndk_lts (i686-linux-android)	57s
quiche_ios (aarch64-apple-ios)	1m 14s
quiche_multiarch (armv7-unknown-linux-gnueabihf)	3m 23s
quiche_multiarch (i686-unknown-linux-gnu)	2m 2s
	55m 53s

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