Adapt chart line output to accept multiple filters

[cozyGalvinism]

As outlined in #77, this is my proposed API change for ChartLineOutputAdapter.lua. I also amended the filter structure to

{
    [1] = {
        name = 'my_metric',
        color = colors.red
    }
}

The only caveat so far is an error that pops up right at the start of series, apparently by a nil value in the plot data? I cannot figure out where it's coming from... It doesn't affect the output but if I can solve it, I will amend the PR.

[cozyGalvinism]

I have fixed the error. It came from the fact that I thought the plotter could draw lines based on their local minimums and maximums, but that doesn't seem to be the case. I have amended the chartLines to use the global minimum and maximum instead and the error resolved itself.

[cyberbit]

Looks to be basically working for me! There are some small changes I will recommend once I figure out how to submit them.

[cyberbit]

Just a few minor changes but otherwise lgtm!

[cyberbit]

Looks great, merged! Thanks again for contributing 🩵