Code duplication in psydata

[hiker]

When implementing #1288 , some functionality (automatically created unique region names) was moved from the Extract node into the transformation. But other transformations (at least profile) still need the same code in the node, not in the transformation, which results in code duplication (I tried to use a common function in the node and transformation, but the tree is in a different state - once before the extract node is inserted, and once where the 'upper' part of the tree has been lowered, making this very hacky).

The special setup in the psydata nodes should consistently be moved into the transformation. Known issues:

• [ ] Creation of unique region names
• [ ] Determining the input- and output-variables (for extraction), it is maintained atm to keep the lfric extraction working.

[hiker]

• [x] After #1483 there should be a proper base class for LFRic- and GOcean driver creation.

[hiker]

I cover the common base class for driver creation in #2049.