The typing of br_table was relaxed in
https://github.com/WebAssembly/spec/pull/1305. Before, we had to compute
the greatest lower bound of all branch types and make sure that stack
values are subtypes of that type. Now, we have to check that the stack
values are subtypes of each individual branch. This makes a difference
only in polymorphic stacks, but greatly simplifies the code, especially
with the upcoming introduction of a much more complex type system in
wasm-gc.

Change-Id: I6e3b410cfe0e71a97623b3030b3575ef707c4900
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2827897
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73982}