feature: update circuit drawing

[jcjaskula-aws]

Issue #, if available:
N, C characters are not conventional to denote (neg)controlled qubits.
Circuits can also look nicer by using box drawing characters.

Description of changes:

• changed N and C to empty/full unicode circle
• use box drawing characters
• keep ascii diagram as legacy builder
• move ascii_circuit_diagram.py and boxdrawing_circuit_diagram to text_circuit_diagram_builders/
• create a text_circuit_diagram.py containing helper functions to reuse common code.

Testing done:
updated unit tests.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (b4245ea) to head (af08fe7).

Additional details and impacted files

@@            Coverage Diff             @@
##              main      #846    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
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  Files          129       132     +3     
  Lines         8618      8814   +196     
  Branches      1928      1987    +59     
==========================================
+ Hits          8618      8814   +196     

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[jcjaskula-aws]

Looks like the wrong character is being used. On mobile it shows up as ⏺️. I believe ● is the correct character.

Was using U+25CB and U+25CF. I could find the large white circle (U+25EF) but not the black one. Eventually, I switch to the character you pasted in your comment and U+25EF, but I still could not find the unicode number for the large black circle.

[krneta]

I'm not crazy about hard-coding these (again?)... couldn't we just have put in the correct symbol on line 131? For SWAP, why are we not just changing the symbol in the class, rather than here?

[jcjaskula-aws]

I'm concerned that gates like Cnot have harcoded ascii_symbol = ["C", "X"] that will be passed through L124. If we want to keep AsciiCircuitDiagram and UnicodeCircuitDiagram living together, I believe it is easier to transform control qubit symbols as late as possible.

I think it is also better to transform SWAP later than earlier. If we change the ascii_symbol, we will need an exception in _draw_symbol because we should avoid boxing the symbol x (which will look like an x gate then).