Vendor tools dram tests were not enabled until #1234 got merged.

With SymbiFlow/symbiflow-arch-defs#1268 I have temporarily disabled the vivado_targets, to let CI go green (as it has been red for too long now).

This issue is to keep track of the problem with DRAM evaluated on vendor tools with fasm2bels.

Current save/load methods focus on dumping and loading the pipeline definition in its JSON form, but provide no means to save a fitted pipeline and load it later to make predictions, being the usage of pickle outside of the pipeline the only way to go.

Let's re-implement the save/load methods to save the whole pipeline instance, and move the current save functionality to a to_json method.

Expected Behavior

ItemAt(IEnumerable<T> source, int position, T fallback) delivers the element at the given position (or the fallback)
A test should cover this.

Actual Behavior

ItemAt(IEnumerable<T> source, int position, T fallback) delivers the element at the first position and not at the given position.

Mention any other details that might be useful

By the way: The do

For consistency with others, toJSON() should be added to the address types.