json: Store short strings in-place. #3269

Job	Run time
libreswan (ubuntu-24.04)	5s
dpdk gcc (ubuntu-24.04)	7s
linux rpm fedora	4m 3s
linux deb no dpdk	4m 57s
osx clang --disable-ssl	1m 29s
build oss-fuzz fuzzers	3m 2s
linux gcc --disable-ssl	3m 4s
linux clang --disable-ssl	2m 28s
linux gcc c99	2m 36s
linux clang c99	2m 32s
linux gcc test	8m 40s
clang-analyze-cache	12m 35s
linux clang address,undefined test	16m 25s
linux gcc test --enable-shared	11m 51s
linux clang test --enable-shared	12m 22s
linux gcc check check-dpdk dpdk	18m 42s
linux clang check check-dpdk dpdk	18m 16s
linux gcc test -ljemalloc	9m 11s
linux clang test -ljemalloc	9m 4s
linux gcc --enable-afxdp	4m 32s
linux clang --enable-afxdp	4m 47s
linux gcc dpdk --enable-shared	5m 6s
linux clang dpdk --enable-shared	3m 40s
linux gcc dpdk-shared	4m 43s
linux clang dpdk-shared	4m 8s
linux gcc dpdk-shared --enable-shared	5m 49s
linux clang dpdk-shared --enable-shared	3m 44s
linux gcc m32 --disable-ssl	2m 35s
linux gcc check-ovsdb-cluster	6m 29s
linux gcc check-kernel -100	12m 1s
linux gcc check-kernel 100-	16m 51s
linux clang address,undefined check-kernel -100	12m 59s
linux clang address,undefined check-kernel 100-	21m 45s
linux gcc check-offloads -100	12m 5s
linux gcc check-offloads 100-	11m 58s
linux gcc dpdk check-system-userspace	12m 15s
linux clang address,undefined dpdk check-system-userspace	16m 2s
linux gcc dpdk check-system-tso	12m 9s
linux gcc dpdk check-afxdp	13m 57s
clang-analyze	10m 53s
	5h 39m 57s

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