ovsdb-idl: Add a way to assert IDL txn as read only. #2960

Job	Run time
libreswan (ubuntu-24.04)	7s
dpdk gcc (ubuntu-24.04)	9s
build oss-fuzz fuzzers	2m 47s
linux rpm fedora	3m 58s
linux deb no dpdk	12m 22s
osx clang --disable-ssl	2m 12s
clang-analyze-cache	12m 48s
linux clang --disable-ssl	5m 21s
linux clang address,undefined test	17m 25s
linux gcc c99	3m 57s
linux gcc test	10m 51s
linux gcc check check-dpdk dpdk	21m 11s
linux gcc --disable-ssl	4m 35s
linux clang test --enable-shared	12m 5s
linux gcc dpdk-shared	4m 43s
linux gcc m32 --disable-ssl	5m 19s
linux gcc test -ljemalloc	9m 43s
linux gcc dpdk-shared --enable-shared	5m 32s
linux gcc --enable-afxdp	3m 58s
linux clang c99	4m 31s
linux clang --enable-afxdp	3m 1s
linux clang dpdk --enable-shared	6m 19s
linux gcc test --enable-shared	13m 17s
linux clang dpdk-shared	6m 0s
linux gcc check-kernel -100	16m 16s
linux clang check check-dpdk dpdk	19m 55s
linux clang address,undefined check-kernel -100	15m 14s
linux clang dpdk-shared --enable-shared	4m 25s
linux clang address,undefined check-kernel 100-	24m 30s
linux gcc check-ovsdb-cluster	8m 33s
linux clang test -ljemalloc	9m 33s
linux gcc dpdk --enable-shared	4m 25s
linux gcc check-kernel 100-	22m 24s
linux gcc dpdk check-system-userspace	13m 26s
linux gcc check-offloads 100-	18m 7s
linux gcc dpdk check-system-tso	14m 37s
linux gcc dpdk check-afxdp	14m 44s
linux clang address,undefined dpdk check-system-userspace	19m 32s
linux gcc check-offloads -100	10m 3s
clang-analyze	12m 43s
	6h 40m 38s

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