fix: multi-line inline block with background color; support CSS filter

[Ovilia]

Summary

This PR fixes/implements the following bugs/features

• Bug: multi-line inline block with background color
• Bug: CSS filter was not supported

Explain the motivation for making this change. What existing problem does the pull request solve?

Bug 1: multi-line inline block with background color

Before:

The background of multi-line inline element has wrong position, and it covers other text.

After:

Bug 2: CSS filter has no effect

Before:

CSS filter was not supported.

After:

Test plan (required)

• tests/reftests/filter.html
• tests/reftests/text/child-textnodes.html

Code formatting

Please make sure that code adheres to the project code formatting. Running npm run format will automatically format your code correctly.

Closing issues

Fixes #

[ghost]

However, this test case is failing - there's an issue with the textBounds calculation:

<div 
  class="text-formatting" 
  style="border: 1px solid transparent; border-radius: 10px"
>
  <div style="color: #fae1e1">
    <mark 
      data-color="#a64242" 
      style="background-color: #a64242; color: inherit"
    >
      <u>Financial freedom is achieved when passive income covers living expenses, requiring</u>
      test
    </mark>
    <s>
      <mark 
        data-color="#a64242" 
        style="background-color: #a64242; color: inherit"
      >
        <u>clear goals, planned paths and seizing opportunities. Core strategies include increasing income and reducing expenses, investment management and career development. Combined with Ganzhou's distinctive economy such as rare earth and cultural tourism industries, one can</u>
      </mark>
    </s>
    <mark 
      data-color="#a64242" 
      style="background-color: #a64242; color: inherit"
    >
      <u>discover unique opportunities to accelerate wealth accumulation.</u>
    </mark>
  </div>
</div>

The textBounds calculation has issues with this complex nested structure.

[Ovilia]

Financial freedom is achieved when passive income covers living expenses, requiring test clear goals, planned paths and seizing opportunities. Core strategies include increasing income and reducing expenses, investment management and career development. Combined with Ganzhou's distinctive economy such as rare earth and cultural tourism industries, one can discover unique opportunities to accelerate wealth accumulation.

Thanks for your feedback. I don't think this is a problem brought by this PR because I checked the result with the currect code before this PR, it behaves the same. So I think this should be relevant to my changes.