Meta+headless-browser: Add support for crash tests

[tcl3]

This PR adds support for both our own internal crash tests and allows us to import crash tests from WPT. These are essentially the same as text tests, but they have no associated expectation file. These tests pass if the test fully loads without crashing.

NOTE: The WPT runner uses WebDriver to execute this script when running crash tests. We don't currently do this, which may lead to some imported tests finishing before they've been given the opportunity to crash. I haven't included an equivalent mechanism in this PR, as it complicates the import processes and didn't seem necessary for some crash tests I tried to import while testing.

Advances: #2282

[shannonbooth]

I do worry a little that this could result in crash tests being imported which dont actually end up testing anything, and causing confusion if we have partial support for it. Especially for those who follow the specifics of our test harness less closely.

Maybe we should make it a bit more involved to import a crash test?

[shannonbooth]

This might hold less weight than I think though, part of this is coming from my experience with https://github.com/LadybirdBrowser/ladybird/pull/2081/files which is such a weird test case that it might be a bit of an exception compared to most other crash tests since it really messes with the document.

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[AtkinsSJ]

This looks good to me, is there something preventing it being merged?