Use instance methods for type()

[Ms2ger]

Currently, the explainer has static methods, to be used like

const t = WebAssembly.Table.type(table);

rather than the rather more ergonomic

const t = table.type();

Apparently this was inspired by Object static methods such as Object.keys. However, the main reason to put new APIs on the Object constructor rather than the prototype (AFAIK) is to avoid collisions with instance properties. That doesn't apply here - we don't really expect people to put arbitrary properties on these objects. In any case, these interfaces already have all of their API on the prototype, so putting the new methods would be more consistent with that as well.

[rossberg]

The other reason to make reflection API static is to be more mirror-like, in order to properly separates object capabilities from meta capabilities. That is less relevant for the Wasm API, though.