Add destructure pattern parser

[jfmengels]

In breaking-changes-v8, we have a separate type and parser for parser destructure patterns. I figured we could backport it to master without changing the type.

A benefit of having this already in the master branch is that rebase of the v8 branch will be smaller too, and we can continue to improve the performance of it until v8 lands.

I've updated it over successive rebases to resemble the regular Pattern parser, so it should have similar performance, or actually faster since it tries less things. My gut feeling says that this should therefore be faster, but in practice I measure a 1 to 3% performance decrease (using find-regressions), which I find surprising. Maybe it's not run enough times and therefore the JIT doesn't optimize as much or enough? 🤔

What do you think?