Bug - MenuToggle - aria labelling doesn't work as intended

定位 MenuToggle 的实现、其 props 接口，以及 issue 中链接的 React Select 示例。检查当前如何渲染 aria-label、aria-labelledby 和动态 toggle 文本，然后更新组件和示例，使内部 button 具有所需的 accessible name。使用 single-select 示例和 VoiceOver 验证生成的 markup。

Describe the problem
Per https://github.com/patternfly/patternfly/issues/6562, we need to update how aria labeling is handled in MenuToggle, namely:

• Right now the aria-label on the MenuToggle does nothing since the text content is taking precedence,

• We need to ensure MenuToggle's with dynamic text content have an accessible name that includes a static label as well as the dynamic toggle content

How do you reproduce the problem?
Go to a MenuToggle and Select example and navigate both with VoiceOver. Notice that only the text content gets announced. Then choose a new option in the Select example, and notice that there's no context for what the Select is actually for but rather just the current text content.

Expected behavior
Note this is most likely only for a non-typeahead and non-plain MenuToggle, basically only a MenuToggle whose content would be dynamic like in Select examples (where by default the toggle content may be "Choose an option", then choosing an option updates the toggle content to e.g. "Option 1").

• MenuToggle should have an aria-labelledby on its internal button element that should reference the pf-v6-c-menu-toggle__button (if aria-label is passed; if aria-labelledby is passed to MenuToggle then this internal aria-labelledby should reference that ID instead) and pf-v6-c-menu-toggle__text elements -- this should only occur when aria-label or aria-labelledby are passed to MenuToggle

• We should add aria-labelledby to the props interface to explicitly expose it

• Examples using MenuToggle must be updated so that there is a unique/descriptive static label as well as its content label

Using the single select example in React, here's what the markup should end up looking similar to:

Is this issue blocking you?
List the workaround if there is one.

Screenshots
If applicable, add screenshots to help explain the issue.

What is your environment?

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

What is your product and what release date are you targeting?

Any other information?

Jira Issue: PF-1729