AdGuard Home makes copies of local filters

We should inspect whether this is necessary. If not, it's better to not waste resources and disk space on that.

Original message:

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On the filepath-based filters, it seems that it still makes copies of local filters lists. I even made it with the exact name and local it is saved, and refreshing makes it overwrite the list with itself. Prabably that could be improved, not making copies of local lists, because it causes unnecessary writing to the router flash...

```
Thu Mar 23 18:41:17 2023 daemon.err AdGuardHome[4640]: 2023/03/23 18:41:17.783850 [info] saving filter 1679514854 contents to: /opt/AdGuardHome/data/filters/1679514854.txt
```

_Originally posted by @cjom in https://github.com/AdguardTeam/AdGuardHome/issues/5606#issuecomment-1481782822_