This patch adds support for parsing structs in the type section.
It also removes the assumption that all types in the type section are
function types, adding appropriate validation.
Spec tests struct.3 and struct.4 have been disable as this would
require expanding `ValueType` to include more heap-types.
This, along with moving the sources and destination out of the config
object, makes it so we don't have to double-deref to get to them on each
instruction, leading to a ~15% perf improvement on dispatch.
The spec tells us to reject the promise with a RuntimeError instead of a
LinkError whenever the module's start function fails during module
instantiation. Fixes 1 WPT subtest in `wasm/core`.
...instead of specially handling JS::Completion.
This makes it possible for LibWeb/LibJS to have full control over how
these things are made, stored, and visited (whenever).
Fixes an issue where we couldn't roundtrip a JS exception through Wasm.
