Convert os.path to pathlib based Paths #1121

Job	Run time
Build MDANSE and run tests on ubuntu-latest	3h 27m 56s
Build MDANSE and run tests on ubuntu-latest	13m 26s
Build MDANSE and run tests on ubuntu-latest	10m 47s
Build MDANSE and run tests on ubuntu-latest	10m 47s
Build MDANSE and run tests on ubuntu-latest	10m 5s
Build MDANSE and run tests on ubuntu-latest	10m 5s
Build MDANSE and run tests on ubuntu-latest	11m 5s
Build MDANSE and run tests on ubuntu-latest	11m 5s
Build MDANSE and run tests on windows-latest	16m 46s
Build MDANSE and run tests on windows-latest	16m 46s
Build MDANSE and run tests on windows-latest	16m 53s
Build MDANSE and run tests on windows-latest	16m 53s
Build MDANSE and run tests on windows-latest	16m 18s
Build MDANSE and run tests on windows-latest	16m 18s
Build MDANSE and run tests on windows-latest	17m 18s
Build MDANSE and run tests on windows-latest	17m 18s
Build MDANSE and run tests on macOS-latest	11m 3s
Build MDANSE and run tests on macOS-latest	11m 3s
Build MDANSE and run tests on macOS-latest	8m 0s
Build MDANSE and run tests on macOS-latest	8m 0s
Build MDANSE and run tests on macOS-latest	7m 45s
Build MDANSE and run tests on macOS-latest	7m 45s
Build MDANSE and run tests on macOS-latest	8m 3s
Build MDANSE and run tests on macOS-latest	8m 3s
	8h 9m 28s

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