Improve screenreader UX for audio player placeholder

[gavinspence]

Is your feature request related to a problem? Please describe.
We've recently introduced a loading indicator placeholder in place of the audio player on our radio and podcast pages. This is to better inform those on slower devices and connections that a media player is loading instead of just showing a white space.

We've broken out some of the accessibility requirements as we require translations in order to complete them.

Describe the solution you'd like
For services that have audio pages, ensure the screenreader UX is correct and we read out 'audio player loading'.

Given I use a screen reader
And I am viewing a page with the audio player
When the audio player loading indicator is displayed
And I navigate to this element
Then this content is announced as “Audio player loading” (translated)
And no HTML semantics are announced (as it’s a strong element which doesn’t convey semantics)
And is announced in the content order in the same position as the audio player would be

Given I use a screen reader
And I am viewing a page with the audio player
When the audio player loading is complete
Then I should not be able to navigate to content announced as “Audio player loading” (translated)

Translations have been requested on #wstranslations for the following services:

• afaanoromoo
• afrique
• amharic
• arabic
• bengali
• burmese
• gahuza
• hausa
• hindi
• indonesia
• korean
• kyrgyz
• marathi
• nepali
• pashto
• persian
• portuguese
• russian
• somali
• swahili
• tamil
• tigrinya
• urdu
• uzbek
• zhongwen/simp
• zhongwen/trad

Describe alternatives you've considered
NA

Testing notes
[Tester to complete]

Dev insight: Will Cypress tests be required or are unit tests sufficient? Will there be any potential regression? etc

• This feature is expected to need manual testing.

Additional context
Add any other context or screenshots about the feature request here.