lognorm distributions failing when using callable pars.

[RHull-IDM]

Both lognorm_ex and lognorm_im currently fail when passed a callable parameter.

To reproduce:

import starsim as ss
import sciris as sc
import numpy as np

sim = sc.prettyobj()
sim.n = 10
sim.people = sc.prettyobj()
sim.people.uid = np.arange(sim.n)
sim.people.slot = np.arange(sim.n)
sim.people.age = np.random.uniform(0, 90, size=sim.n)

def custom_mean(module, sim, uids):
    out = sim.people.age[uids]
    return out

testdist = ss.lognorm_ex(mean=custom_mean, stdev=2).initialize() # fails with TypeError: '<=' not supported between instances of 'function' and 'int'

testdist2 = ss.lognorm_im(mean=custom_mean, sigma=np.log(2)).initialize() # fails with TypeError: loop of ufunc does not support argument 0 of type function which has no callable exp method

[cliffckerr]

Closed by #527