Add checkbox to Settings > Media to control whether to generate JPEG in addition to WebP

[mehulkaklotar]

Summary

This PR is dependent on the issue #524 and PR #527

PR introduces

• WordPress setting generate_webp_and_jpeg -> boolean value
• Changes default filter output for webp_uploads_upload_image_mime_transforms to image/jpeg and image/webp if the generate_webp_and_jpeg is true

Remaining work(After #524 is merged)

• Add unit tests around new WP Settings and their use with filter
• Changes if needed any from the dependent PR Generate only WebP images by default for JPEG and WebP uploads #527

Fixes #525

Relevant technical choices

Checklist

• PR has either [Focus] or Infrastructure label.
• PR has a [Type] label.
• PR has a milestone or the no milestone label.

[mehulkaklotar]

@mukeshpanchal27 Changes looks good here. We should add some tests for the new setting.

[felixarntz]

@mehulkaklotar This is on a good path, some quirks to address though.

[felixarntz]

@mehulkaklotar One more thing: Please make sure to delete the new option in uninstall.php.

[felixarntz]

@mehulkaklotar This is almost good to go now. Left mostly minor suggestions, so there are two quirks (one little tricky) to still address.

[felixarntz]

@mukeshpanchal27 @mehulkaklotar One small optimization recommendation here, but other than that this is good to go.

[felixarntz]

Thanks @mukeshpanchal27, LGTM!