In this commit I have added input (and explicit output) compatibility
between pymapdl-reader and the pathlib.Path class. All file path-input
arguments should now be accepted as either strings or pathlib.Path
objects. Additionally there is no breaing change regarding the filename
properties. These will continue to return strings. Wherever possible I
have made it so that internally we store paths as pathlib.Path objects
and they are returned as strings through properties. Setters
additionally will accept strings or pathlib.Path objects.

Unfortunately i have not been able to get the test suite working on my
local machine and so have not been able to write tests to go with these
changes. I would appreciate input from others regarding how to get the
tests running and if my changes do break any existing tests. I do not
believe so but I am very limited in how I can check.

Changed the suffix comparison to include the leading '.' because
pathlib.Path.suffix does include it. Made sure that AnsysFile converts
any potential paths to string before they are passed as arguments.

Additionally split thermal test up until multiple tests within a class
to make it easier to read.

All existing tests pass with pathlib changes.

Added additional tests to check the input and output is correct for the
4 classes that use pathlib.Path now.