fix: sp-split-button more button label

[jnurthen]

Fixes #3305

Description

Changes the label for the more button from static text to a reference to the sibling button element

Related issue(s)

#3305

Motivation and context

How has this been tested?

• Test case 1
  1. Go to https://jnurthen-issue3305--spectrum-web-components.netlify.app/components/split-button/
  2. Inspect the more part of the split button and look at the Accessible Name in Dev tools
  3. Note that it should be the same as the accessible name of the button part of the split button

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (minor updates related to the tooling or maintenance of the repository, does not impact compiled assets)

Checklist

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• If my change required a change to the documentation, I have updated the documentation in this pull request.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.
• I have reviewed at the Accessibility Practices for this feature, see: Aria Practices

[github-actions]

Branch Preview

• Documentation Site
• Storybook

Visual regression test results

When a visual regression test fails (or has previously failed while working on this branch), its results can be found in the following URLs:

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[github-actions]

Tachometer results

Chrome

split-button permalink

Version	Bytes	Avg Time	vs remote	vs branch
npm latest	671 kB	2035.63ms - 2039.26ms	-	unsure 🔍 -0% - +0% -2.46ms - +2.46ms
branch	671 kB	2035.79ms - 2039.10ms	unsure 🔍 -0% - +0% -2.46ms - +2.46ms	-

Firefox

split-button permalink

Version	Bytes	Avg Time	vs remote	vs branch
npm latest	671 kB	2163.10ms - 2176.86ms	-	unsure 🔍 -7% - +2% -169.94ms - +49.78ms
branch	671 kB	2120.42ms - 2339.70ms	unsure 🔍 -2% - +8% -49.78ms - +169.94ms	-

[Westbrook]

Firefox appears to ship a slightly different accessibility tree in response to these updates. Can you take a look at the difference and update either the implementation or the test case here?

[Westbrook]

@jnurthen this gets the test passing in Firefox. Not sure if this counts as a bug in Firefox (or possibly in Playwright, they're deprecating these API anyways 😢), but it seems to be OK on our end.

If it's good for you, I'm good to merge this in.

[jnurthen]

thanks for fixing that. That looks good.

[Westbrook]

LGTM. Thanks for getting this cleared up for us!