Logscale fixes in scatter, pcolormesh and imshow

[nvaytet]

Fixes the case where ax.set_xscale('log') is called before the artist is added to the axes.
This should now work:

import numpy as np
import matplotgl.pyplot as plt

x, y = np.random.normal(size=(2, 50_000))

fig, ax = plt.subplots()

ax.set_xscale('log')
ax.scatter(x, y)

fig