[Visualisation] Known qadence.draw issues

[RolandMacDoland]

• Latex strings: graphviz cannot deal with latex natively. one (the only) solution is to generate SVGs that can be used as icons. there is code that does almost all of the work in qadence.draw.utils, just alignment in different outputs (png/svg/notebook) has to be fixed. also, this becomes very slow for circuits with many gates, because for every gate we have to compile a fresh svg (via latex). caching svgs based on hashes of expressions could be a solution here
• bending wires: when drawing tags (in graphviz clusters) around blocks that contain control gates/identities the nodes are sometimes squeezed together which leads to bending of circuit wires. this could either be solved by setting node height=1, or (probably the worse solution) by generating icons for identity/control nodes which have the same height as the other nodes.
• if the outermost block is tagged the tag is not displayed.