Prioritize custom rules over other rules

### Prerequisites

- [X] I have checked the [Wiki](https://github.com/AdguardTeam/AdGuardHome/wiki) and [Discussions](https://github.com/AdguardTeam/AdGuardHome/discussions) and found no answer

- [X] I have searched other issues and found no duplicates

- [X] I want to request a feature or enhancement and not ask a question

### Description

#### What problem are you trying to solve?
I have a whitelist that allows graph.instagram.com using the rule '@@|*graph.instagram.com^' but I want to block it while still keeping the whitelist. However even if I add '||graph.instagram.com^$important' to my custom filtering rules it is not prioritized. Anything with the $important flag in custom filtering rules should be prioritized.