W-17609247 - Fix Safari bug where the same image loads several times

[vcua-mobify]

This PR addresses a known Safari bug seen also in other systems (such as this from Next.js).

The bug in Safari is that if an image has the src attribute before srcSet and sizes, it will fetch the image multiple times as it processes each attribute.

To ensure Safari only loads an image once, we set src to be the last attribute.

Reproducing the original issue:

1. In Safari, open dev tools
2. Go to https://pwa-kit.mobify-storefront.com/global/en-GB/product/Spring-look-2M (or deploy a version of the PWA without this fix onto an MRT test environment)
3. In the network tab, search for PG.10236198.JJ3KRXX.PZ
4. See that there are multiple requests to fetch this image (the first one without any query parameters and the second one with ?sw={width}&q=60)

You can compare this result with Chrome (which only loads the image once with ?sw={width}&q=60)

Testing the fix:

1. Deploy this fix onto MRT and in Safari navigate to the same page on your test environment (or go to https://scaffold-pwa-vincentc-test-env.mobify-storefront.com/global/en-GB/product/Spring-look-2M)
2. In the network tab, search for PG.10236198.JJ3KRXX.PZ
3. See that there is now only one request to fetch the image (the one with ?sw={width}&q=60)

[vmarta]

Please add a code comment to explain why and to make sure that src will be kept last.

[vmarta]

In the test environment, I've verified that the bug fix works as expected on Safari browser 👍

[joeluong-sfcc]

Confirmed on the test env that there is no duplicate image requests