Update Next-Gen gallery compatibility for AVIF support

[remyperona]

Description

Update Next-Gen gallery compatibility for AVIF support

Type of change

• Bug fix (non-breaking change which fixes an issue).

Code style

• I wrote self-explanatory code about what it does.
• I wrote comments to explain why it does it.
• I named variables and functions explicitely.
• I protected entry points against unexpected inputs.
• I did not introduce unecessary complexity.

[Mai-Saad]

Exploratory test notes
Next-gen gallery plugin
Already on 2.1.3 (may need separate GH)
1- At next gen gallery, expand /collapse view details isnot working
2- Click restore original image, then click optimize again, will show that image is already optimized instead of optimizing it (tested with large image, and with med image but with medium image webP won't be created for main image 'only for thumb' while delete webp option is displayed in NGG page)
3- optimizing in nextgen gallery view will keep loading till manual refresh the page
4- image not optmized in media but optimized on next gen gallery

5- open bulk page at next -gen gallery will result in
[19-Mar-2024 09:03:17 UTC] PHP Deprecated: Function _imagify_display_bulk_page() is deprecated since version 1.7! Use Imagify_Views::get_instance()->display_bulk_page() instead. in /home/mai/Local Sites/imagifynginx6/app/public/wp-includes/functions.php on line 6078 => added GH #862

6- Generated next-gen is yes for this image although webp no generated for main image

7- Restore original isnot clickable while generate webp link is there

8- The new size > original size and both != that in media library (if generate webP is off , new size < original but still != that in media library)

9- Progress bar in bulk optimization of next gen gallery is 0 while the chartbar is != 0

10- imagify all keeps loading after being clicked in next-gen bulk optimization although % is 100 till manually refresh the page

on 2.2.0.1 already
#863

on 2.2.1

• enable avif after uploading n images at next-gen will result in generating -n/0 (keeps loading ) in settings page of imagify. @piotrbak do we need to fix this on PR or it needs other GH? (similar issue was already fixed in media library when disable avif, however, it's happening in next-gen gallery when enable/disable avif) => agreed to be different issue

[Mai-Saad]

Test report
testrail-report-587.pdf
failed test due to the point mentioned on 2.2.1 above ..

[piotrbak]

@Mai-Saad As we talked, we'll be good here. 1st and 5th point will deserve the separate GH, the same for the one you meantioned as the last point on 2.2.1