fix: improve side filtering to match tokens rather than substrings

[gagnonanthony]

I stumbled on a small issue with side filtering when plotting commissural bundles: when the bundle filename contained r_ or l_, it was incorrectly assigned to a hemisphere, whereas it should appear in both. See below for an example where the filename was CC_Fr_1.trk:

I simply changed how side filtering was performed: tokenize the filename, then match side patterns. It now does not catch trailing substrings (e.g., r_ or l_):

The filtering steps also still work for truly lateralized bundles (assuming either left, right, l, r, lh, or rh is in the filename).

[teanijarv]

Thanks! I did a minor edit to one line and also replicated same approach to plot_subcortical()