Add support for disabling per-filetype ImageFormatLoader import

[Spartan322]

This was the simplest way I could conceive of to address #69085 (comment), this would pave the way to restore functional DDS runtime image loading without the import process messing them up. If should_import() returns false then it'll be skipped for ImageLoader::get_recognized_extensions() when p_import is true. (which is every case that function is called except for Particles2DEditorPlugin's constructor from what I can see)

[RandomShaper]

I'm not sure this is the right approach.

If I'm understanding correctly, the issue here is we need a list of all the extensions corresponding to image types the engine will load succesfully. Wouldn't just asking that to the ResourceFormatImporter with the right resource type work?

[RandomShaper]

Closed by accident due to my mouse pointer drifting for a second.

[Spartan322]

I'm not sure this is the right approach.

Yeah I am still unsure myself coming up with it, I'm trying to ponder what would make the best solution but this was the least involved I could think of.

Wouldn't just asking that to the ResourceFormatImporter with the right resource type work?

I'm not sure how it could do that since the importers don't have any way to distinguish what should and shouldn't be imported for filetypes (all they care about is that it has an ImageFormatLoader) which is where the issue lies as DDS files would still be some form of a texture resource type, it can only figure that out based on the extensions given by ImageLoader::get_recognized_extensions. And since there isn't really anything that distinguishes the filetypes for the importers outside the extensions, I'm not sure how it be expected to pass the respective ImageFormatLoader to be called by an importer.