One final PR for some setup and helper code related to the LAMA to Dask migration (#182) before I start pushing up the actual method migrations in turn!

This one adds a temporary custom decorator that will be applied to directly mark methods that we consider to have been migrated fully in the code, so we don't have to cross-reference with the very long checklist in the issue (though I will make sure to update the list too upon each corresponding merged PR). As well as acting as a marker, the decorator provides a log message reported each time the method is run (which can be adapted to provide more info, as useful) and allows the log level to be tuned for those methods only by simply changing the decorator argument value.

I have marked all methods considered 'daskified' after @davidhassell's initial work with the decorator and will add it incrementally to other methods as they are completed.

Example of resulting test output change

By running pytest test_Data.py -rP (the options of which I have found useful so far), STDOUT is captured, e.g. under the configuration of this branch state it returns:

============================= test session starts ==============================
platform linux -- Python 3.8.10, pytest-6.2.4, py-1.10.0, pluggy-0.13.1
rootdir: /home/sadie/cf-python
collected 73 items                                                             

test_Data.py ssss.s..ss.s.s.ssssssssssssssss.sssssssssssssssssssssssssss [ 80%]
ssssssssssssss                                                           [100%]

==================================== PASSES ====================================
________________________ DataTest.test_Data___setitem__ ________________________
------------------------------ Captured log call -------------------------------
WARNING  cf.data.data:data.py:155 %%%%% Running daskified hardmask %%%%%
WARNING  cf.data.data:data.py:155 %%%%% Running daskified __setitem__ %%%%%
WARNING  cf.data.data:data.py:155 %%%%% Running daskified shape %%%%%
...
...
WARNING  cf.data.data:data.py:155 %%%%% Running daskified array %%%%%
WARNING  cf.data.data:data.py:155 %%%%% Running daskified hardmask %%%%%
WARNING  cf.data.data:data.py:155 %%%%% Running daskified size %%%%%
...
...
======================== 7 passed, 66 skipped in 0.98s =========================

though the minimal test output report of pytest can be recovered by removing the -rP options, and/or converting the arguments to daskified() to sto the message output.

Overall I'm setting us up for some major debugging sessions that will probably be required in later stages of the migration 😄