[FIX] - Add fix for special case of rdsym

[TomDonoghue]

For sim_asine_cycle, there are special cases of rdsym value that can lead to an off by one error in terms computing the number of samples in the cycle. This comes from how we compute the number of samples based on rdsym value.

For example, on main, the following code would get the wrong sample length (101 instead of 100):
cyc = sim_asine_cycle2(0.1, 1000, 1., side='both')

This can happen for 'peak' or 'both' when rdsym is 1., and for 'trough' when rdsym is 0.

This PR adds a check and fix for this issue, as well as some extra tests to keep an eye on this issue (note that these tests would fail on current main branch).

[ryanhammonds]

This is still an issue when rdsym = .999. There is also another potential bug I found when digging into this. When the trough is asymmetrical, the symmetrical side deviates from expected I think. This isn't an issue when the peak is asymmetrica:

import matplotlib.pyplot as plt
from neurodsp.sim.cycles import sim_asine_cycle

rdsym = .8

plt.plot(sim_asine_cycle(0.1, 1000, rdsym, side='peak'), label='Peak Asym')
plt.plot(sim_asine_cycle(0.1, 1000, rdsym, side='trough'), ls='--',label='Trough Asym')
plt.plot(sim_asine_cycle(0.1, 1000, .5, side='both'), ls='--', label='Sym')
plt.legend()

I think the alternative implementation below fixes the off-by-one samples issue and the side='trough' issue above. It uses scipy's sawtooth to create the phase array instead of stacking linspace arrays.

def sim_asine_cycle2(n_seconds, fs, rdsym, side='both'):

    check_param_range(rdsym, 'rdsym', [0., 1.])
    check_param_options(side, 'side', ['both', 'peak', 'trough'])

    # Determine number of samples
    n_samples = compute_nsamples(n_seconds, fs)
    half_sample = int(n_samples/2)

    # Create phase of asine
    time_asym = np.linspace(0, 2*np.pi, n_samples+1)[:-1] + np.pi * rdsym
    phase = sawtooth(time_asym, rdsym) * np.pi * .5
    
    # Create phase of sine
    if side != 'both':
        time_sym = np.linspace(0, 2*np.pi, n_samples+1)[:-1] + np.pi * .5
        phase_sym = sawtooth(time_sym, .5) * np.pi * .5
        
    if side == 'peak':
        phase[half_sample:] = phase_sym[half_sample:]
    elif side == 'trough':
        phase[:half_sample] = phase_sym[:half_sample]
        
    # Convert phase definition to signal
    cycle = np.sin(phase)

    return cycle