[BUG]: `scattergl` text is hidden behind selected markers

[Lexachoc]

Description

scattergl text is hidden behind selected markers

The equivalent scatter trace renders the text correctly.

Reproducible example:

https://codepen.io/Lexachoc/pen/dPvRydx

    mode: "markers+text",
    texttemplate: "x=%{x}",
    selectedpoints: [0],
    selected: {
      textfont: { color: "red" }
    },
    unselected: {
      textfont: {color: 'white'}
    },

---

For unselect.textfont, both works, only select.textfont is broken for scattergl:

Note

To confirm, uncomment

textposition: 'top-center',

Additional warning observed

When using:

 mode: "markers+text",

or

 mode: "text",

scattergl will throw this warning:

Canvas2D: Multiple readback operations using getImageData are faster with the willReadFrequently attribute set to true. See: https://html.spec.whatwg.org/multipage/canvas.html#concept-canvas-will-read-frequently

caused by this line: var bottomPx = firstTop(ctx2.getImageData(0, 0, l2, l2)); from the vendor package.

Reported before in #7285