feat: add loading a11y to s3 selectors for screen readers

[orangevolon]

Description

Adds Last Updated to the S3 resource selector modal.
The addition of this text should help the screen readers to inform the users once the fetch process is finished.

Related links, issue #, if available: AWSUI-41521

How has this been tested?

Manually tested on Chrome, Firefox & Safari.
Automated testing in progress.

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.80%. Comparing base (d7217eb) to head (f82ac50).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2475      +/-   ##
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- Coverage   95.80%   95.80%   -0.01%     
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  Files         728      728              
  Lines       19874    19886      +12     
  Branches     6700     6745      +45     
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+ Hits        19040    19051      +11     
- Misses        779      827      +48     
+ Partials       55        8      -47     

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[avinashbot]

Just a random comment - it's crazy to me that we don't disable the reload button while a fetch is taking place. But at this point, I'm a little worried that switching it to a loading state is a breaking change, so... 😔

[orangevolon]

It certainly looks weird not receiving a feedback when clicking on the button. I think here the other parts of the "loading & refreshing" guideline also comes into play.

Cases for when it's loading, it's taking longer that usual or it's failing for some reason.
I think it makes sense to bucket them together, in another PR.