feat: add seismic-alloy-trie minimal crate (part of no-trie-fork)

[samlaf]

DO NOT MERGE

We probably will want to only merge this after the audit is done, unless we decide we want to pull the trigger and want it audited.

This adds a new minimal seismic-alloy-trie wrapper crate around alloy-trie. alloy-trie has functions to compute the storage state root, but they take into<U256> as arguments. We want to be passing FlaggedStorage, so instead of forking alloy-trie like we previously did, I'm adding equivalent functions here that we should use in reth (and foundry?) instead.

See design in https://hackmd.io/ZOGfcUP2SyKmPeOuz0tmvg

[samlaf]

TODO: points to SeismicSystems/seismic-alloy-core#58

[samlaf]

Still not 100% sure what's the best / less error-prone design here. The issue with having this is that reth could forget in some place to use this one and instead use the stock alloy-trie's storage_root_unashed, passing it an unshielded FlaggedStorage by mistake.

What we could do is to re-export all of alloy-trie (except for these functions; thereby forcing downstream consumers to use these Into variants) as part of this crate (similar to how the alloy monorepo re-exports alloy-core).

[samlaf]

Claude analysis:

That's a reasonable approach. But consider an even simpler option first: can you just shadow the function name?                                          
                  
  If seismic-alloy-trie re-exports a storage_root() that takes FlaggedStorage, and seismic-reth depends on seismic-alloy-trie (which it already does), then
   anyone doing use seismic_alloy_trie::storage_root gets the correct version. The upstream alloy_trie::storage_root still exists but nobody should be
  importing from alloy_trie::root directly — and you can grep for that.                                                                                    
                  
  But if you want a compile-time guarantee, your fork approach works. The minimal change would be:

  1. Keep seismic-trie as a thin fork of alloy-trie
  2. Remove storage_root(), storage_root_unsorted(), storage_root_unhashed() from the ethereum feature
  3. Keep TrieAccount, state_root_*(), ordered_trie_root*() — those are fine and widely used
  4. The seismic-alloy-trie crate provides the replacement storage_root() with FlaggedStorage

  That way, any code that accidentally calls alloy_trie::storage_root() gets a compile error. The fork diff is tiny — just deleting 3 functions — and easy
  to maintain across upstream updates.

  You don't even need a separate seismic feature flag for this. Just delete those 3 functions from the ethereum module. They're convenience helpers, and
  the only correct version now lives in seismic-alloy-trie.