CI: clean test dirs, reset `collisionXZ` checksums #19553

Job	Run time
GCC ABLASTR w/o MPI	36s
GCC Minimal w/o MPI	15m 10s
GCC 3D & RZ w/ MPI, single precision	5m 1s
GCC 1D & 2D w/ MPI, QED tools	2m 16s
save_pr_number	5s
Clang pywarpx	7m 9s
Clang UB sanitizer	40m 39s
	1h 10m 56s

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