fix(exex): skip missing notification files when filling the WAL block cache

[jowparks]

A hole in the ExEx WAL file ID range currently makes the node unbootable: fill_block_cache walks min..=max and propagates WalError::FileNotFound out of Wal::new, aborting startup. Warn and skip the missing file instead; other WalError variants still abort.

Hit on the Base shadow builder, which crash-looped on boot until <datadir>/exex/wal was deleted by hand:

called `Result::unwrap()` on an `Err` value: notification 251460 not found

Holes are reachable because WalInner::commit consumes the next file ID before writing, so a failed write (the shadow builder had filled its SSD) burns the ID permanently. Not addressed here.

Second commit fixes two unrelated clippy lints in reth-network that a newer toolchain flags; they fail CI on this branch regardless of this change. deny is also red on this branch for RUSTSEC-2026-0258 (h2), which needs a lockfile bump and is out of scope here.

[jowparks]

Closing in favour of an upstream report: paradigmxyz#26813.

The diagnosis in this PR is wrong about the cause. It blames WalInner::commit burning a file id when a write fails (full disk). That path is real but rare, and is not what we hit.

The actual cause is Wal::finalize. BlockCache::notification_max_blocks is a min-heap keyed by (max_block, file_id), so remove_before evicts by block number while file ids are assigned by write order. A ChainReverted from an execution-stage unwind carries the abandoned fork's high tip, which pins those files while later, lower-height commits get evicted from underneath them — deleting a file from the middle of the id range. The read path then assumes min..=max is dense and startup dies. No disk failure involved.

There is a deterministic unit test in the upstream issue that reproduces this on unmodified main with no filesystem tampering.

The warn!-and-skip fix here is still roughly the right shape, but it is option 2 of 3 upstream; enumerating the ids that actually exist is the better fix. Leaving that to upstream rather than carrying a fork patch built on a wrong rationale.

Branch jowparks/exex-wal-skip-missing-notification stays pushed if we need to revive it.