Disable post-MVP Wasm features

[tomaka]

Close #217

It's unclear to me whether sign-ext and Non-trapping float-to-int conversions should be disabled as well. See paritytech/substrate#10707 (comment).

[github-actions]

twiggy diff report

Difference in .wasm size before and after this pull request.

---

 Delta Bytes │ Item
─────────────┼──────────────────────────────────────────────────────────────────────────────────────
        -183 ┊ <wasmi::engine::Engine as core::default::Default>::default::h3c493386f3d4acb5
        +138 ┊ smoldot::executor::vm::interpreter::InterpreterPrototype::new::h657255d0b93b4b88
        +136 ┊ <wasmi::engine::config::Config as core::default::Default>::default::h51acb3769bb26f13
         +13 ┊ wasmi::engine::config::Config::wasm_bulk_memory::h298fdff5a68bd003
         +13 ┊ wasmi::engine::config::Config::wasm_extended_const::hb703c453ded2d9f2
         +13 ┊ wasmi::engine::config::Config::wasm_multi_value::h7dd41a6ece67399f
         +13 ┊ wasmi::engine::config::Config::wasm_mutable_global::h3f380dd6f8ad5446
         +13 ┊ wasmi::engine::config::Config::wasm_reference_types::h50300a32d2158107
         +13 ┊ wasmi::engine::config::Config::wasm_saturating_float_to_int::he9f95d8a168a4fe5
         +13 ┊ wasmi::engine::config::Config::wasm_sign_extension::he0d7e712a68c2281
         +13 ┊ wasmi::engine::config::Config::wasm_tail_call::hd204389c1737a7e1
          +3 ┊ elem[0]
        +805 ┊ Σ [12 Total Rows]