Flexible Sequence drawing

[HGSilveri]

• Makes the detuning curve appear only when the detuning is being used (i.e. is not zero throughout the channel)
• Adds the option to draw the phase in a curve (draw_phase_curve) in drawing methods
• Simplifies the color scheme for programmed vs modulated waveforms by using a hatch on output waveforms instead.

Examples:

• Bell state creation sequence, which uses only resonant pulses so the detuning curve is automatically omitted

• The phase curves show up when draw_phase_curve=True. The detuning is still omitted if not used (as happens for the"raman_local"` channel)

To Do:

• The phase curves are for now being extracted by the _seq_drawer.gather_data() function, as is still the case for the amplitude and detuning. As outlined in Sequence sampler feature extension #349, we would like these to come from the sampler instead.
• There is some freedom in the moment the phase is changed that can be used to minimize the number of phase jumps and the effects of modulation. This should also be done centrally by the sampler.

Closes #332 .

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[CdeTerra]

Some general style remarks, to be discussed and that could be applied later.

[HGSilveri]

@CdeTerra I agree with your remarks in general, I admit I tend to be more careless with functions for plotting because I don't expect people to read their contents often, but it's a bad habit. I'll give your suggestions a shot before merging, if I find they're not so hard to implement I'll still include them here.

[CdeTerra]

Good changes! Small new comments, but approving in general.