Since expression evaluation is now done via an EvalContext method, and
since these tests use the MockEvalContext, we need to provide a value for
the mock call to return. Previously expression evaluation happened at a
different layer that was not mocked here.
After the refactoring to integrate HCL2 many of the tests were no longer
using correct types, attribute names, etc.
This is a bulk update of all of the tests to make them compile again, with
minimal changes otherwise. Although the tests now compile, many of them
do not yet pass. The tests will be gradually repaired in subsequent
commits, as we continue to complete the refactoring and retrofit work.
