Catch up some code style fixes.
Update the call expr parsing tests.

As part of the refactoring to support an intermediate representation the
AST model of a call was changed to support both positional and named
arguments, so this catches up the parser tests to match with the new
model.
Remove the defunct AST-oriented execute/codegen tests.

We're no longer doing execution or codegen against the AST, but instead
the intermediate form. Therefore all of the AST execute/evaluate/generate
functions are now defunct, allong with their associated tests.