Phase out get-connected-net

[tjknoth]

Eventually we will probably delete this, for now I:

• added an introspection get-connected-nets that returns all connected net statements
• changed make-via-grid to just net directly to the target object
• changed the corresponding field in PortInfo to a tuple
• added a function connected-net on PortInfo that mimics the old functionality (for backwards compatibility)
  Another thing we will need to look at:
  make-thermal-vias assumes the existence of a single net statement for its geom statement. This will often not be true -- it still works since I reimplemented connected-net, but it will arbitrarily select the first net statement. Maybe this is fine, I'm not 100% sure

[callendorph]

👍 Thank you for catching this!