feat(project): use a native fallback for image service

[AntonLantukh]

Description

• Use a native fallback for additional images (via poster_fallback=1 query)
• Store images as a simple string for media items (instead of ImageData object)
• Add backward compatibility for ImageData structure for channels / programs not to force customers to update all their schedules

This PR solves # .

Steps completed:

According to our definition of done, I have completed the following steps:

• Acceptance criteria met
• Unit tests added
• Docs updated (including config and env variables)
• Translations added
• UX tested
• Browsers / platforms tested
• Rebased & ready to merge without conflicts
• Reviewed own code

[github-actions]

Visit the preview URL for this PR (updated for commit 302b23b):

https://ottwebapp--pr328-feat-simplify-altern-g1ccvisf.web.app

_{(expires Thu, 17 Aug 2023 15:54:34 GMT)}

_{🔥 via Firebase Hosting GitHub Action 🌎}

_{Sign: c198f8a3a199ba8747819f7f1e45cf602b777529}

[ChristiaanScheermeijer]

Nice cleanup. I've left two small comments/questions

[AntonLantukh]

@ChristiaanScheermeijer Do you know any cases where shelfImageAspectRatio is used by customers? I would just leave aspectRatio.

[dbudzins]

I don't mind keeping the more verbose param. What was the reason for the name change in the first place? Just aspectRatio might imply the sizing of the shelf itself.

[AntonLantukh]

We use now cardImage instead of shelfImage as we changed the label to card by default (AC). Previously shelfImage custom param was used to define the label. I can also use cardImageAspectRatio.

[ChristiaanScheermeijer]

I don't think so. We're using this in the demo app configs, though. But if you are going to change it and remove the fallback, it would be good to mention it in the changelogs.

[AntonLantukh]

Left the fallback withshelfImageAspectRatio (deprecated), added cardImageAspectRatio