Render an aria-label for the initial mini cart html

[alexflorisca]

Changes proposed in this Pull Request:

This PR renders an aria-label attribute for the initial mini-cart html that gets rendered, before React kicks in and replaces it.

Closes #42289 .

How to test the changes in this Pull Request:

1. Use a block theme and ensure you have the mini cart in the header template part, both for the Header and Checkout Header template parts
2. Visit the site on the front-end and disable javascript in your browser (In chrome, you can open up the developer tools and press CMD + SHIFT + P and type "disable javascript")
3. Inspect the Mini Cart Icon.
4. Check the button element has an 'aria-label' attribute that says "Cart"
5. Add some items to your cart and go to the Checkout page
6. Open up the developer tools and search for the mini-cart element (You can search for "mini-cart" in the Elements tab)
7. Check that it is not visible on the page, but that it has an aria-label property that says "Cart"

[github-actions]

Hi @wavvves,

Apart from reviewing the code changes, please make sure to review the testing instructions as well.

You can follow this guide to find out what good testing instructions should look like:
https://github.com/woocommerce/woocommerce/wiki/Writing-high-quality-testing-instructions

[github-actions]

Test using WordPress Playground

The changes in this pull request can be previewed and tested using a WordPress Playground instance.
WordPress Playground is an experimental project that creates a full WordPress instance entirely within the browser.

Test this pull request with WordPress Playground.

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[wavvves]

LGTM! but be sure to add the missing changelog file before merging ;)