[click_helper][ResourceOption] Allow exceptions when loading entry points

So far the ResourceOption class tried to load a string as entry points
and would do this in a while loop. But sometimes an option may accept
both objects and some special strings like the dask client which can be
both "single-threaded", "threaded", and Client objects. Addition of
string_exceptions allows for this kind of special cases to be implemented.
2 jobs for string_exceptions in 5 minutes and 48 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #219100
docker
build_linux_37

00:02:40

73.0%
passed #219099
macosx
build_macosx_37

00:05:48

74.0%