Remove deprecation warnings and associated code for previous config structures

[riley-harper]

There are several deprecation warnings sprinkled throughout the code that warn about previous config structures. The code around these warnings handles the previous structures for for backwards compatibility. We can remove these as we move forward with the new config structure. This is technically a breaking change and goes nicely with the planned configuration upgrades, so this can happen in hlink v4.

The deprecation messages are...

• The config value 'blocking_steps' has been renamed to 'blocking' and is now just a single array of objects (matching)
• The config value 'column_mappings' is no longer a nested (double) array and is now an array of objects (preprocessing)
• The 'mapping' transform no longer takes the 'values' parameter with a list of mappings in dictionaries; instead each mapping should be its own transform (core)