$important option doesn't work if domains are not prefixed by || #954

Prerequisites

• I verified that this is not a filter issue
  • Filter issues MUST be reported at filter issue tracker
• This is not a support issue or a question
  • Support issues and questions are handled at /r/uBlockOrigin
• I performed a cursory search of the issue tracker to avoid opening a duplicate issue
  • Your issue may already be reported.
• I tried to reproduce the issue when...
  • uBlock Origin is the only extension
  • uBlock Origin with default lists/settings
  • using a new, unmodified browser profile
• I am running the latest version of uBlock Origin
• I checked the documentation to understand that the issue I report is not a normal behavior

Description

$important option does not override exception filters unless its prefixed by ||example.com, in other words a rule like
/path/ads$important,domain=example.com|example.org
doesn't override the exception and this behavior is not explained in wiki.

A specific URL where the issue occurs

https://9to5mac.com/

Steps to Reproduce

1. Go to the site with EasyList enabled and
   /wp-content/*/prebid$script,important,domain=9to5google.com|9to5mac.com|9to5toys.com|electrek.co|dronedj.com
   added to My Filters and also logger opened.
2. See the request to the resource was allowed.
3. If you have a rule like
   ||9to5mac.com/wp-content/*/prebid$script,important
   it will be blocked.

Expected behavior:

$important should override any exception.

Actual behavior:

Stated

Your environment

• uBlock Origin version: 1.25.2
• Browser Name and version: Firefox 74.0 / Firefox Android 68.6
• Operating System and version: Windows 10 / Android 10