Check signatures of host functions at initialization and sync functions list with spec

[tomaka]

We now verify the signatures of host functions directly when initializing the prototype.
This removes some error conditions.

Additionally, this PR synchronizes the list of functions that we support with the functions on https://spec.polkadot.network/
All the todo!()s have been removed, meaning that a malicious runtime can no longer make smoldot panic.

[github-actions]

twiggy diff report

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

---

 Delta Bytes │ Item
─────────────┼────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
       +8482 ┊ smoldot::executor::vm::interpreter::InterpreterPrototype::new::h229c5de18112680c
       -1644 ┊ <&T as core::fmt::Display>::fmt::h5c4a02a4a2295041
       +1451 ┊ <&T as core::fmt::Display>::fmt::h185508ba6c8124c3
       -1117 ┊ <smoldot::executor::host::Error as core::fmt::Debug>::fmt::h4bb49b8d0e168c25
        +982 ┊ <smoldot::executor::host::Error as core::fmt::Debug>::fmt::h4803cdfa74cb1f38
        +646 ┊ smoldot::executor::host::Inner::alloc::hcc3b1baec05303f9
        -646 ┊ smoldot::executor::host::Inner::alloc::hfdc086457b5ed935
        -409 ┊ <smoldot::executor::host::Error as core::clone::Clone>::clone::hd3e4a5931d643015
        +369 ┊ <smoldot::executor::host::Error as core::clone::Clone>::clone::hfa2fd1de35d1e19b
        +268 ┊ smoldot::executor::host::ReadyToRun::run_once::h42471b52c5e6c06b
        +137 ┊ smallvec::SmallVec<A>::push::h55d7699780f3e912
        -119 ┊ <smallvec::SmallVec<A> as core::iter::traits::collect::Extend<<A as smallvec::Array>::Item>>::extend::h1a7e2912b57becbd
         +96 ┊ <[A] as core::slice::cmp::SlicePartialEq<B>>::equal::h62fc1a2d21b5a4c3
         +96 ┊ data[0]
         -64 ┊ core::ptr::drop_in_place<smoldot::executor::host::Error>::h55ae9a9a7d78c599
         -64 ┊ core::ptr::drop_in_place<smoldot::executor::host::Error>::hbb85a40a09c24296
         +63 ┊ core::ptr::drop_in_place<smoldot::executor::host::Error>::h62370c71bc2efa8f
         +63 ┊ core::ptr::drop_in_place<smoldot::executor::host::Error>::h72ea5e81da3b7104
         +46 ┊ smoldot::executor::host::HostFunction::name::h25167ff83f10661c
         -46 ┊ smoldot::executor::host::HostFunction::name::he4c9ce98bf187fc6
         -42 ┊ ... and 6 more.
       +8716 ┊ Σ [26 Total Rows]