Improve shared module error/warning reporting
The "not found" and "version check" messages were removed for the initial implementation of auto-installing shared
modules due to technical details, but now that the auto-install logic lives in the webstore installer this can be restored.
Add install warnings when extensions are loaded unpacked and have unrecoverable errors regarding shared modules.
Also clean up a few messages to read better with extension names instead of IDs where possible.
BUG=274845
Review URL: https://codereview.chromium.org/
423223002
Cr-Commit-Position: refs/heads/master@{#298082}