testrunner: do not load `std.cfg` in executor tests #19300

Job	Run time
build_cmake (alpine:3.23, false, false)	4m 6s
build_make (ubuntu:25.10)	3m 34s
build_make (ubuntu:24.04)	2m 52s
build_cmake (ubuntu:24.04, true, true)	2m 58s
build_cmake (ubuntu:25.10, true, true)	2m 58s
build_make (alpine:3.23)	5m 54s
	22m 22s

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