Update to newest tifffile

[ecobost]

tifffile (the library we use in the background for loading the files) has changed quite a bit since late 2019 (the version we currently use). It might be worth to update it for performance, bug fixes or new features

This requires

1. making sure that all tests are passes (i.e., everything still works) if tifffile is updated (there are some reported breaking changes introduced but they seem to be small, say different data types or extra returned arguments and so on)
2. see whether new features or changes in tifffile can be taken advantage of to simplify our code or to improve performance.