Fixed #242 - Integration Notes

This MR is an implementation of the changes needed to use multiple snippets, as described in https://gitlab.com/eyeo/adblockplus/adblockpluscore/-/issues/227#integration-note, but it's also needed to make https://gitlab.com/eyeo/adblockplus/adblockpluscore/-/issues/200 work as expected.

As previously discussed, since we can run N snippets at once, we've decided to drop any cached related mechanism.