Revert "ResourceLoader: Report error if resource type unrecognized"

[akien-mga]

• This reverts commit fe21913 / PR ResourceLoader: Report error if resource type unrecognized (reverted) #97370.
• Fixes "Open Anyway" on missing dependency no longer works, reports "File '<file_name>' is saved in a format that is newer that the formats supported by this version of Godot, so it can't be opened." #99467.
• Reopens ResourceLoader.load_threaded_get_status returns THREAD_LOAD_LOADED after ResourceLoader.load_threaded_request with invalid path #95490.

PR #97370 actually seems benign and correct, but it seems to be exposing a pre-existing issue when the r_error code is now set and bubbles up. Ideally we'd just give this a bit of time to find a fixup, but we're about to build 4.4-dev5 right now and would prefer not to have a known regression on refactoring in an update that's centered around refactoring (UIDs).

So we're doing a quick revert for now, to re-try that PR (third time's the charm!) later on. CC @RandomShaper