LibWasm: Clean up module sections API

Remove `for_each_section_of_type` in favor of making the module's
sections defined as distinct fields. This means it is no longer possible
to have two of the same section (which is invalid in WebAssembly, for
anything other than custom sections).

Userland/Libraries/LibWeb/WebAssembly/WebAssembly.cpp

@@ -182,7 +182,7 @@ JS::ThrowCompletionOr<NonnullOwnPtr<Wasm::ModuleInstance>> instantiate_module(JS
             TRY(import_name.type.visit(
                 [&](Wasm::TypeIndex index) -> JS::ThrowCompletionOr<void> {
                     dbgln("Trying to resolve a function {}::{}, type index {}", import_name.module, import_name.name, index.value());
-                    auto& type = module.type(index);
+                    auto& type = module.type_section().types()[index.value()];
                     // FIXME: IsCallable()
                     if (!import_.is_function())
                         return {};