This changes the split from AssignmentPattern and BindingPattern to Pattern and
BindingPattern. Pattern collects all errors that are invalid in both assignment
and binding pattern contexts. Binding pattern additionally collects errors for
binding pattern contexts (property access isn't a valid target). The
distinction is piggybacked on to distinguish assignment vs binding pattern
errors since binding pattern verification will first throw the binding pattern
error.

Since we don't throw pattern error as binding pattern as well, this can mean
that a later binding pattern syntax error will show up before an early pattern
error. Since that just changes the message to another syntax violation, I think
that's fine.

Change-Id: Ib6a22c8d11c49eacc6667ae8ee5e98bababadd43
Reviewed-on: https://chromium-review.googlesource.com/c/1349273Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57774}