[Fix] Improve fallback behavior for `chartSequentialColors`

[mayagbarnes]

Describe your changes

Previously, chartSequentialColors had to be passed exactly 10 valid colors to be applied since sequential colors are used to create a continuous gradient (see streamlit_plotly_theme.py). This PR updates the behavior so passing less than 10 or greater than 10 colors still works, but as follows:

• If chartSequentialColors receives less than 10 colors, it repeats the colors from the beginning until it has 10 color values
• If chartSequentialColors receives more than 10 colors, only the first 10 values are used

Testing Plan

• Unit Tests (JS and/or Python): ✅ Added
• E2E Tests: ✅ Added
• Manual Testing: ✅

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[jrieke]

If chartSequentialColors receives less than 10 colors, it repeats the colors from the beginning until it has 10 color values

Hm I'm not sure if this makes so much sense here given that these colors should be sequential? E.g. if I pass in 5 colors from blue to white, it would be pretty awkward (and also potentially hard to debug) if my values go from blue -> white -> blue -> white. Or am I understanding something wrong here?

Maybe we should rather raise an exception or interpolate between the colors?

Edit: yeah looking at the test screenshots I think it is pretty confusing that e.g. 0 and 4 have the same color. I don't think that's something you'd ever want in a sequential chart.