Auto merge of #11791 - craftytrickster:11712/pipeline-lookup, r=asajeffrey

Pipeline lookup in webdriver

Fixes #11712

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Removed a method that seemed to duplicate already existing functionality, and returned BrowsingContextErrors in the web_handler file where panics were previously occurring.

I am not sure if I like all the unwrapping that occurs in the script thread, but the current methods are not set up to return Option/Result.

Also, should line the method on line 37 `find_node_by_unique_id` of components/script/webdriver_handlers.rs return None if the context is not found like I have it currently? Or should it return a `Result<Option...>` instead?

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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #11712 .

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- [ ] There are tests for these changes OR
- [X] These changes do not require tests because I simply removed a method that duplicated already existing functionality. On the other part, I added better error sending instead of forcing a panic, which does not require testing to my knowledge.

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