DesignSpaceCfg: add getInstance

Added a shortcut for creating an instance using one or more parameter
configurations.
CodeMappingCfg: add getInstance

Added a shortcut for creating an instance using one or more mappings.
Add Helper
AdvancedSingleRangeNextTest: add nested references

Testing references to array elements and nested parameters.
Helper: add gen and sink test functions

- Update a sink test case with a param builder.
- Update a gen test case with a param builder.
- Update a gen test case with multiple parameter configurations.
Moved tests from RangeTest to SetValueTest

Now longer uses a parameterized runner, so individual test cases have
names. Removed commented out illegal cases. These are already handled
elsewhere.
Helper: add design factory method

Added a function that takes one or more ParamCfg and returns a design.
ConfigValidator: remove unused import
Added FixedNumericTest