Fix #3544, Allow multiple ancestors to be encapsulated with svelte class in case of ambiguity

[jesseskinner]

I've fixed issue #3544 by allowing for multiple ancestors to match a selector, in the case that the ancestors have eg. dynamic classes and it's non-deterministic which of the ancestors will match.

I removed the filter that enforced only the first and last node to be encapsulated, so now multiple nodes are able to be encapsulated for a single selector-node pairing.

I didn't want to lose the optimization of skipping inner matches, so I had to change the logic so that it iterates over all blocks and ancestors until it finds the outermost non-global block that matches one or more ancestors. We include all the matching ancestors and then also include the child node.

apply_selector was originally written as a recursive function, but I chose to refactor out part of this into a block_might_apply_to_node function so that we're able to compare whether an ancestor node might match a selector block without doing it recursively.

Any feedback is very much welcome! This is my first time working with this code base so if there's anything I should have done differently, please let me know.

Thanks!

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Tests

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[jesseskinner]

Two more notes I forgot to mention:

1. I removed the Spreadsheet argument to apply_selector because it was unused.
2. I was unable to get npm run lint to run properly, it might be broken in the latest version?

[jesseskinner]

@Conduitry I've added an enum and removed the TypeError, let me know what you think.