feat(l1): implement debug_storageRangeAt RPC endpoint

[azteca1998]

Summary

• Adds debug_storageRangeAt which iterates storage slots for a contract address starting from a given key
• Returns up to maxResult entries with a nextKey for pagination
• Uses the block's final state root; txIndex-based state reconstruction is a future enhancement
• Preimage lookup not yet available (original key field returned as null)
• Matches geth's debug_storageRangeAt

Closes part of #6572

Test plan

• Returns storage entries for a known contract
• Pagination via nextKey works correctly
• Unknown address returns empty result
• Invalid block hash returns error

[github-actions]

⚠️ Known Issues — intentionally skipped tests

Source: docs/known_issues.md

Known Issues

Tests intentionally excluded from CI. Source of truth for the Known
Issues section the L1 workflow appends to each ef-tests job summary
and posts as a sticky PR comment.

EF Tests — Stateless coverage narrowed to EIP-8025 optional-proofs

make -C tooling/ef_tests/blockchain test calls test-stateless-zkevm
instead of test-stateless. The zkevm@v0.3.3 fixtures are filled against
bal@v5.6.1, out of sync with current bal spec; the broad target trips ~549
fixtures. Re-broaden once the zkevm bundle is regenerated.

Why and resolution path

PR #6527 broadened
test-stateless to extract the entire for_amsterdam/ tree from the
zkevm bundle and run all of it under --features stateless; combined with
this branch's bal-devnet-7 semantics that scope produces ~549
GasUsedMismatch / ReceiptsRootMismatch /
BlockAccessListHashMismatch failures.

test-stateless-zkevm filters cargo to the eip8025_optional_proofs
suite, which still validates the stateless harness without the bal-version
mismatch.

Re-broaden by switching test: back to test-stateless in
tooling/ef_tests/blockchain/Makefile once the zkevm bundle is regenerated
against the current bal spec.

[github-actions]

Lines of code report

Total lines added: 130
Total lines removed: 0
Total lines changed: 130

Detailed view

+--------------------------------------------------------+-------+------+
| File                                                   | Lines | Diff |
+--------------------------------------------------------+-------+------+
| ethrex/crates/networking/rpc/debug/mod.rs              | 5     | +1   |
+--------------------------------------------------------+-------+------+
| ethrex/crates/networking/rpc/debug/storage_range_at.rs | 127   | +127 |
+--------------------------------------------------------+-------+------+
| ethrex/crates/networking/rpc/rpc.rs                    | 1303  | +2   |
+--------------------------------------------------------+-------+------+