Make visual changes for 0 and 1 control values [unitaryhack]

[ankit27kh]

Context:
Text drawing had no difference between 0 and 1 control values. Similarly, mpl drawer was missing ControlledQubitUnitary in its special cases
Description of the Change:
Changes text drawer to have different symbols for 0 and 1 control values. Also, add ControlledQubitUnitary as a special case in mpl drawer. Adds logic in mpl drawer to consider control_values
Benefits:
Better visual circuits.
Possible Drawbacks:

Related GitHub Issues:
Closes #2660

[codecov]

Codecov Report

Merging #2668 (634bd07) into master (189de28) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #2668   +/-   ##
=======================================
  Coverage   99.58%   99.58%           
=======================================
  Files         249      249           
  Lines       20220    20228    +8     
=======================================
+ Hits        20137    20145    +8     
  Misses         83       83           

Impacted Files	Coverage Δ
pennylane/drawer/tape_mpl.py	100.00% <100.00%> (ø)
pennylane/drawer/tape_text.py	100.00% <100.00%> (ø)

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[ankit27kh]

Hey @albi3ro, I think this is ready

[albi3ro]

I just realized we didn't update the documentation examples, but I can do that this afternoon. The documentation changes will be easy but extensive because many examples rely on qml.draw to demonstrate their behaviour.

Thanks for the great suggestion and contribution @ankit27kh ! This will especially be useful going forward as we make our control operations more general.

[ankit27kh]

Hey @albi3ro, I found another discrepancy with the mpl drawer. While out of the scope of this PR, it is still something you may want to look at when generalising control operations.
I have made bug report #2677.