Type hinting improvements - mypy conformance

[ADBond]

Decreasing the number of mypy errors Getting the code to pass mypy, mainly through adjusting type hints and renaming variables.

I have added a github workflow for type-hinting - under the assumption that I probably won't fix all the issues in this PR, I will switch it off before requesting review, and then switch on when doing further work, leaving it on eventually when it's all sorted which is now passing. If it is too prohibitive for the moment, we can always disable it while we get things tightened up.

Have also cut out some of mypy checking, for now, to make it easier to build up to full conformance in pieces (slowly adding in all modules + rules).

More substantial changes:

• Settings is now always dialected
• fix some logic in SettingsCreator.from_path_or_dict
• split out and slightly simplified the logic for getting cluster ids in cluster_studio if not supplied
• SplinkDataFrame now an abstract base class
• misc.read_resource has guard for missing file
• test for tf_adjustment_chart

Note on @final and property/setters - these doesn't really work with mypy, so there is no way (afaict) to properly guard these against being overridden by subclasses. What you can do is @final after @some_att.setter, and mypy will be happy, but it will not complain if subclasses overwrite this. Have left it there as at least a hint to devs that they shouldn't implement these, even if it won't be enforced by mypy.

From 148 errors down to 0.