[BUG]: word caps skips the first word after <br>, and mock text decorations depend on the Chrome version #8120

Description

textcase: "word caps" doesn't capitalize the first word after a <br> when the line before ends with a letter. All lines share one <text> element, so text-transform: capitalize reads "set<br>two" as the word "settwo".

Screenshots

Steps to reproduce

• Open Plotly devtools and paste the following into the browser devtools console:

Plotly.newPlot(gd, [{ y: [1, 2] }], {
    font: { textcase: 'word caps' },
    shapes: [{ type: 'line', x0: 0, x1: 1, y0: 1, y1: 2, label: { text: 'not set<br>two lines' } }]
});

• Note that the second line isn't capitalized

Notes

• Treemap and icicle slices without text draw a ' ' placeholder with the trace font. With lineposition, Chrome 154 draws a stray underline dash under that space.
• Chrome 155 skips decorations under spaces at the start or end of a line. Thus geo_africa-insets, text_on_shapes_basic, and treemap_multi-line_headers render differently in Chrome 154 and Chrome 155.
• GitHub runner images recently started using the newer version of Chrome, but not all of them so we're seeing intermittent CI failures
• For now, I'm going to pin Chrome. Once the version rolls out across all runners, we'll need to address this issue.