CarpetX: make driver.hxx and schedule.hxx visible to other thorns #1349

Job	Run time
download-build-test (cpu, real32, debug)	12m 3s
download-build-test (cpu, real64, debug)	12m 10s
download-build-test (cpu, real64, optimize)	17m 40s
download-build-test (cuda, real32, debug)	22m 59s
download-build-test (cuda, real64, debug)	23m 53s
download-build-test (cuda, real64, optimize)	24m 0s
download-build-test (rocm, real64, optimize)	20m 11s
download-build-test (oneapi, real64, optimize)	29m 49s
	2h 42m 45s

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