Use objects qualified name in caching

[bdilday]

This adds a CI stage to illustrate the problem mentioned here #267 #221
namely that when the cache is enabled, the call to get the fangraphs batting and pitching stats return the same dataframe.

[bdilday]

Updated the MR to include a proposed fix for the issue of batting and pitching stats returning the same dataframe.

• moves the cache decorator for the fetch method from the abstract base class FangraphsDataTable to the concrete classes FangraphsBattingStatsTable, FangraphsFieldingStatsTable, FangraphsPitchingStatsTable

this means the fully qualified name will include the concrete class name (e.g. FangraphsBattingStatsTable.fetch) not the base class (e.g. FangraphsDataTable.fetch

• when hashing the function name for caching, uses the fully qualified name (if it doesn't contain <locals>) instead of just the name. this means it will be e.g. FangraphsBattingStatsTable.fetch instead of fetch