Waveform renderer disappears for FSM signals and string reprs

[isabelburgos]

See this link for an example in Amaranth Playground.

After running a simulation including an FSM, going to the waveform tab causes the page to become blank. d3-wave gives the error "None of the installed renderers supports signalType".
Existing d3-wave signal renderers are here and could be extended to support FSM state signals with strings as values.

[whitequark]

This also applies to string reprs.

[mringwal]

Does this also happen when trying to use Memory?