Fix Merkle proof whose trie root node is inferior to 32 bytes being considered as invalid

[tomaka]

Right now, we either hash each proof entry or take its inline value if it is too small.

This isn't correct, for two reasons:

• The root node is always hashed, meaning that right now if the root node of a proof is < 32 bytes, its hash won't be found in our array.
• Nodes that are < 32 bytes should be inlined. There's no situation where a node whose length is < 32 bytes has its own proof entry.

Consequently, we don't care about inline values and just hash the node entries.
We also check whether hashed nodes shouldn't have been inlined, although this is very secondary.

[mergify]

Automatically approving tomaka's pull requests. This auto-approval will be removed once more maintainers are active.

[github-actions]

twiggy diff report

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

---

 Delta Bytes │ Item
─────────────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────────
       +2565 ┊ smoldot::trie::proof_decode::decode_and_verify_proof::h1cffd33ed69ebc9d
       +2506 ┊ smoldot::trie::proof_decode::decode_and_verify_proof::h9ffc573852081119
       -2463 ┊ smoldot::trie::proof_decode::decode_and_verify_proof::h5c31ae1fa26995f9
       -2405 ┊ smoldot::trie::proof_decode::decode_and_verify_proof::habbc8cd40df51711
       +2251 ┊ smoldot::trie::proof_decode::decode_and_verify_proof::he41abb3713a2be8a
       -2160 ┊ smoldot::trie::proof_decode::decode_and_verify_proof::h7e12c78f2c78eca0
        +925 ┊ hashbrown::raw::RawTable<T,A>::reserve_rehash::ha0af7cf21503f8b1
        -925 ┊ hashbrown::raw::RawTable<T,A>::reserve_rehash::hced81ff0d47e0d3b
        -359 ┊ <core::iter::adapters::copied::Copied<I> as core::iter::traits::iterator::Iterator>::fold::h81672765b8599dba
        -359 ┊ <core::iter::adapters::copied::Copied<I> as core::iter::traits::iterator::Iterator>::fold::hb7e1198b11f51578
        +351 ┊ <core::iter::adapters::copied::Copied<I> as core::iter::traits::iterator::Iterator>::fold::h2fe9e27552cf89e9
        +351 ┊ <core::iter::adapters::copied::Copied<I> as core::iter::traits::iterator::Iterator>::fold::h4812cb82e4b0423b
        +323 ┊ hashbrown::map::HashMap<K,V,S,A>::insert::h2de84c1dd47abab3
        -293 ┊ hashbrown::map::HashMap<K,V,S,A>::insert::h46aeb76ef17f9cc4
        +279 ┊ <&T as core::fmt::Display>::fmt::h6b203cc1a0222d54
        +274 ┊ <smoldot::trie::proof_decode::Error as core::fmt::Display>::fmt::h276ea898fd96ccac
        -255 ┊ <&T as core::fmt::Display>::fmt::h75b017ebb1232177
        -250 ┊ <smoldot::trie::proof_decode::Error as core::fmt::Display>::fmt::h2f3cbe64314f996c
        +229 ┊ <smoldot::trie::proof_decode::Error as core::fmt::Debug>::fmt::hb8cd282f4114f61a
        -205 ┊ <smoldot::trie::proof_decode::Error as core::fmt::Debug>::fmt::h254a73bc70e22e14
        -444 ┊ ... and 68 more.
        -814 ┊ Σ [88 Total Rows]