Fix SMT encoding of structs which contain a single struct field #8880

Job	Run time
check-ubuntu-20_04-cmake-gcc	30m 15s
check-ubuntu-20_04-make-clang	27m 10s
check-ubuntu-20_04-make-clang-smt-z3	5m 55s
check-ubuntu-20_04-make-gcc	45m 56s
check-macos-11-make-clang	36m 37s
check-macos-12-cmake-clang	50m 52s
check-ubuntu-20_04-cmake-gcc-KNOWNBUG	3m 37s
check-ubuntu-20_04-cmake-gcc-THOROUGH	9m 52s
check-ubuntu-22_04-cmake-gcc-13	22m 27s
check-ubuntu-22_04-cmake-gcc-32bit	22m 42s
check-ubuntu-22_04-cmake-gcc	46m 56s
check-ubuntu-22_04-make-clang	23m 52s
check-docker-image	24m 18s
check-string-table	3m 52s
check-vs-2019-cmake-build-and-test	1h 17m 22s
check-vs-2022-make-build-and-test	1h 9m 33s
codecov-coverage-report	47m 22s
include-what-you-use	29m 11s
windows-msi-package	37m 30s
	10h 15m 19s

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