Image Loader: roll back to MV2

The image loader extension was recently upgraded to MV3 but there have
been some dev-channel bug reports. M130 branches in a few days.

It's not easy to flip between MV2 / MV3 with a runtime flag or a 10%
experiment. Instead, this commit manually rolls back all of:

https://crrev.com/c/5769997
https://crrev.com/c/5839223
https://crrev.com/c/5850892

But also, in manifest.json, this commit advances the version to "0.4"
instead of rolling back from "0.3.1" to "0.2".

A later commit will undo this one (a roll forward), after M130 branch.

Bug: b:319190834
Test: Manual
Change-Id: I0976f922ad0f2fa64eb2500cb27a811a5f7f5784
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5859075
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Auto-Submit: Nigel Tao <nigeltao@chromium.org>
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1354992}