Fix #14884 fuzzing timeout (hang) in TemplateSimplifier::expandTemplate() #20213

Job	Run time
build_make (alpine:3.23)	5m 56s
build_cmake (alpine:3.23, false, false)	4m 18s
build_make (ubuntu:25.10)	3m 29s
build_cmake (ubuntu:24.04, true, true)	2m 37s
build_cmake (ubuntu:25.10, true, true)	2m 43s
build_make (ubuntu:24.04)	2m 53s
	21m 56s

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