getSkinFile("noavatar.png") broken in Flamingo Skin

Extensions have been using getSkinFile("noavatar.png") and when switching to Flamingo this is broken since apparently the Flamingo skin doesn't provide this resource anymore.

This is a regression breaking extensions.

To name just 2 where I've seen the issue:

• Forum app. Fixed in commit https://github.com/xwiki-contrib/application-forum/commit/3d3a99e5665265607a41d8ce04f38c6ebb8c2d7a
• GitHub Stats Application (problem still there as of now)

We need to decide what to do:

• A) i) Put novatar.png in the Flamingo skin and more generally define the resources that each skin must provide (or better, ii) put it the templates so that if not found in the skin, it can be found in the templates)
• B) Decide that it's a wanted regression and document it properly in the Release Notes
• C) Fall back on /icons/xwiki when getSkinFile() is called and the resource is found neither in the Skin nor in the Templates.

WDYT?