Support prevent-constructor scriptlet

[piquark6046]

https://github.com/AdguardTeam/Scriptlets/blob/master/wiki/about-scriptlets.md#-%EF%B8%8F-prevent-constructor

For example, Resolving uBlockOrigin/uAssets#33021 without every MutationObserver callback needs the scriptlet.

[Yuki2718]

Just FYI https://github.com/uBlockOrigin/uBlock-discussions/discussions/916 but it's in fact better to be an open issue ticket.