Allow turning off minor ticks on Colorbar with LogNorm

PR Summary

Closes #13257.

Allows disabling minor ticks for Colorbar when it has LogNorm.

Before

Minor ticks can be disabled for all norms except LogNorm.

The following example is intended to show that when having arbitrary major tick marks, the minor tick marks add rather than remove confusion. Example,

fig, ax = plt.subplots()

data = np.clip(randn(250, 250)*1000, 0, 1000)

cax = ax.imshow(data, norm=mpl.colors.LogNorm(vmin=1, vmax=1000))
cbar = fig.colorbar(cax, format='%d', ticks=[5, 50, 500])

Produces,

After

Once minor ticks can be disabled even for LogNorm, calling cbar.minorticks_off() will leave only major ticks in the above figure.

Allow minorticks back on for LogNorm as well

Since minor ticks can now be turned off for LogNorm, makes sense to allow turning them back on for LogNorm too.

Previously they would be enabled in ColorbarBase.update_ticks for LogNorm by default, however minorticks_off and minorticks_off was in Colorbar. These have been moved, in part so that update_ticks can take advantage of them.

PR Checklist

• Has Pytest style unit tests
• Code is Flake 8 compliant
• New features are documented, with examples if plot related
• Documentation is sphinx and numpydoc compliant
• Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
• Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way