well-formed: done signals for a group cannot depend on component's input signals

[rachitnigam]

• match_element does not use outside done signal
• check if groups done signal depends on components input signal. Fixes tdcc: Invalid code generated when done depends on input signal #621

[rachitnigam]

Hm, I'm starting to think that this might not actually be the right solution. This doesn't leave us a direct way to pass memories by reference. A group that wants to use a memory by reference needs to add a register to store the done signal.

I'd like to get input from @sampsyo @EclecticGriffin and try to formalize the restriction enforced by well-formed and what the principle behind it is.

[rachitnigam]

We've decided that components should take at least one cycle and a future implementation of combinational primitives will allow them to take less than one cycle. The specific problem with the original TCAM implementation was that it was using a combinational component which currently is not supported by the compilation flow.