Optimize shadow stack storage #362

Job	Run time
linux-x86-deny	48s
linux-x86-ci-generated	13s
linux-native-test-suite (ubuntu-latest)	3m 13s
linux-native-ci-asm (ubuntu-latest)	1m 32s
linux-native-test-suite (ubuntu-24.04-arm)	3m 20s
linux-native-ci-asm (ubuntu-24.04-arm)	1m 18s
windows-x86-ci-asm	3m 3s
linux-x86-ci (ubuntu-latest)	1m 37s
linux-arm-test-suite	5m 47s
linux-x86-ci (ubuntu-24.04-arm)	1m 42s
linux-fuzz	4m 15s
linux-native-ci-asm-chaos (ubuntu-24.04-arm)	1m 24s
linux-native-test-spawn (ubuntu-latest)	1m 44s
linux-native-test-spawn (ubuntu-24.04-arm)	1m 30s
macos-x86-ci-asm	2m 5s
linux-native-ci-asm-chaos (ubuntu-latest)	1m 33s
linux-arm-ci-asm	6m 33s
	41m 37s

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