clients/eels: add EELS Engine API client (amsterdam only)

[spencer-tb]

Adds an eels client definition that runs the execution-specs
(EELS) as an Engine API client, so consume engine and
consume enginex can drive the spec directly. Amsterdam only.

• clients/eels/: Dockerfile (uv image, installs EELS and runs the
  ethereum-spec-engine server from
  feat(spec-specs,tooling): run EELS under hive consume engine for all post-merge forks execution-specs#3363), eels.sh (requires
  HIVE_AMSTERDAM_TIMESTAMP=0, rejects /chain.rlp and /blocks
  imports), hive.yaml with role eth1, stub enode.sh (no p2p).
  No genesis mapper: the server parses the simulator-provided
  genesis file directly. Enginex client reuse works via
  explicit-parent reorgs (the debug rewind probe cleanly reports
  method-not-found).
• simulators/ethereum/eels/consume-engine and consume-enginex:
  add eels to the default disable_strict_exception_matching
  list; there is no eels exception mapper in execution_testing
  yet, so strict matching would reject correct INVALID responses.

Verified against glamsterdam-devnet@v8.1.0 (.*fork_Amsterdam-.*,
24,819 tests): consume-engine smoke 136/136 and consume-enginex smoke
1030/1030 in real hive, ~49k hive test executions across full runs,
and the complete 24,819-test sweep through the exact simulator
sequences locally — all zero failures.

Draft until ethereum/execution-specs#3363 merges; the Dockerfile
then flips its default github/branch build args from the
working fork branch to ethereum/execution-specs.