Add new scriptlets — `xml-prune` and `m3u-prune`

[AdamWr]

Related to this - https://github.com/AdguardTeam/Scriptlets/issues/202, but it shouldn't be a trusted scriptlet. It could be useful in these cases: https://github.com/AdguardTeam/AdguardFilters/commit/c2fc8a1b6f7ee237ec664333d4436e1719da99f8 https://github.com/AdguardTeam/AdguardFilters/commit/de413ca5ff4658c35a8c52efbed98e72a0c4c33f https://github.com/AdguardTeam/AdGuardExtra/issues/297#issuecomment-1172894064

Similar scriptlet in uBlock Origin (I guess that it would be nice to make it compatible with it) - https://github.com/gorhill/uBlock/blob/ec83127f6c628bfa1ed2aeaf7f25873592d3a21f/assets/resources/scriptlets.js#L1672-L1739 and https://github.com/gorhill/uBlock/blob/ec83127f6c628bfa1ed2aeaf7f25873592d3a21f/assets/resources/scriptlets.js#L1743-L1839