Add support for new beacon chain /blobs endpoint

[Tristan-Wilson]

This change adds support for the new beacon chain endpoint /eth/v1/beacon/blobs/{block_id} introduced in Fusaka while maintaining backward compatibility with the legacy endpoint
/eth/v1/beacon/blob_sidecars/{slot}. block_id can be a slot so Nitro just uses slot.

The new endpoint supports server-side filtering by versioned hash via query parameters. Since the Arbitrum sequencer inbox message contains the versioned hashes of the blobs that were posted, we can include those in the query.

Key changes:

• Added UseLegacyEndpoint flag to BlobClientConfig to control which endpoint to use
• Created new GetBlobsBySlot() public method for direct slot-based blob fetching
• Implemented getBlobs() method for the new endpoint with versioned hash verification
• Updated beaconRequest() to support query parameters for filtering
• Added KZG commitment verification when versioned hashes are provided

Created blobtool CLI utility for testing both endpoints:

 # Fetch specific blob using new endpoint (default)
 blobtool fetch --beacon-url=<url> --slot=<slot> --versioned-hashes=<hash>

 # Fetch using legacy endpoint (requires versioned hashes)
 blobtool fetch --beacon-url=<url> --slot=<slot> --versioned-hashes=<hash> --use-legacy-endpoint

 # Compare both endpoints side-by-side
 blobtool fetch --beacon-url=<url> --slot=<slot> --versioned-hashes=<hash> --compare-endpoints

The new endpoint is used by default, with automatic fallback behavior maintained through the existing secondary beacon URL mechanism.

Spec reference: https://github.com/ethereum/beacon-APIs/blob/master/apis/beacon/blobs/blobs.yaml

NIT-3885

Cherry pick of #3826

Testing

To test the new fetching method I added a new tool called blobtool. It's intended to be used for testing beacon endpoints, and it can use either the new or old method for fetching blobs. This is even more important after Fusaka where it is even more difficult to configure beacon nodes to have and keep all blobs. In future we may want to add some features like looking up blobs by block number, which is something operators often want to do.

$ target/bin/blobtool fetch --beacon-url=https://sepolia --slot 8726798                              

Fetching all blobs for slot 8726798 using new blobs endpoint...
Successfully fetched 4 blobs in 550.156533ms
Blob 0: versioned_hash=0x01ac7e2c7fff656a02bb7d8e9934798ab3d1df8fbf20acff5aec87b183fd99cf, size=131072 bytes
Blob 1: versioned_hash=0x01808fa4fb38311c3a2a7c8a37d95af5a18eb3ccfe279d7e02f5df7d839b4a3a, size=131072 bytes
Blob 2: versioned_hash=0x01e0b7530de207b244ce87448a633d7bb077339236d4a4e82985b944553913dc, size=131072 bytes
Blob 3: versioned_hash=0x012873697f6a3baa3ed5b0e53784a2b389fee4c341253a5ef69a85bd720d2aad, size=131072 bytes

$ target/bin/blobtool fetch --beacon-url=https://sepolia --slot 8726798 --versioned-hashes=0x01ac7e2c7fff656a02bb7d8e9934798ab3d1df8fbf20acff5aec87b183fd99cf,0x01808fa4fb38311c3a2a7c8a37d95af5a18eb3ccfe279d7e02f5df7d839b4a3a,0x01e0b7530de207b244ce87448a633d7bb077339236d4a4e82985b944553913dc                               
Fetching 3 blobs for slot 8726798 using new blobs endpoint...
Successfully fetched 3 blobs in 3.075861523s
Blob 0: versioned_hash=0x01ac7e2c7fff656a02bb7d8e9934798ab3d1df8fbf20acff5aec87b183fd99cf (computed=0x01ac7e2c7fff656a02bb7d8e9934798ab3d1df8fbf20acff5aec87b183fd99cf), size=131072 bytes
Blob 1: versioned_hash=0x01808fa4fb38311c3a2a7c8a37d95af5a18eb3ccfe279d7e02f5df7d839b4a3a (computed=0x01808fa4fb38311c3a2a7c8a37d95af5a18eb3ccfe279d7e02f5df7d839b4a3a), size=131072 bytes
Blob 2: versioned_hash=0x01e0b7530de207b244ce87448a633d7bb077339236d4a4e82985b944553913dc (computed=0x01e0b7530de207b244ce87448a633d7bb077339236d4a4e82985b944553913dc), size=131072 bytes

$ target/bin/blobtool fetch --beacon-url=https://sepolia --slot 8726798 --versioned-hashes=0x01ac7e2c7fff656a02bb7d8e9934798ab3d1df8fbf20acff5aec87b183fd99cf,0x01808fa4fb38311c3a2a7c8a37d95af5a18eb3ccfe279d7e02f5df7d839b4a3a,0x01e0b7530de207b244ce87448a633d7bb077339236d4a4e82985b944553913dc --use-legacy-endpoint                             
Fetching 3 blobs for slot 8726798 using legacy blob_sidecars endpoint...
Successfully fetched 3 blobs in 3.254657814s
Blob 0: versioned_hash=0x01ac7e2c7fff656a02bb7d8e9934798ab3d1df8fbf20acff5aec87b183fd99cf (computed=0x01ac7e2c7fff656a02bb7d8e9934798ab3d1df8fbf20acff5aec87b183fd99cf), size=131072 bytes
Blob 1: versioned_hash=0x01808fa4fb38311c3a2a7c8a37d95af5a18eb3ccfe279d7e02f5df7d839b4a3a (computed=0x01808fa4fb38311c3a2a7c8a37d95af5a18eb3ccfe279d7e02f5df7d839b4a3a), size=131072 bytes
Blob 2: versioned_hash=0x01e0b7530de207b244ce87448a633d7bb077339236d4a4e82985b944553913dc (computed=0x01e0b7530de207b244ce87448a633d7bb077339236d4a4e82985b944553913dc), size=131072 bytes

$ blobtool fetch --beacon-url=https://sepolia --versioned-hashes=0x01ac7e2c7fff656a02bb7d8e9934798ab3d1df8fbf20acff5aec87b183fd99cf,0x01808fa4fb38311c3a2a7c8a37d95af5a18eb3ccfe279d7e02f5df7d839b4a3a,0x01e0b7530de207b244ce87448a633d7bb077339236d4a4e82985b944553913dc --compare-endpoints
Comparing legacy blob_sidecars and new blobs endpoints...

Fetching with legacy blob_sidecars endpoint...
✓ Legacy endpoint: fetched 3 blobs in 2.242901587s

Fetching with new blobs endpoint...
✓ New endpoint: fetched 3 blobs in 498.302806ms

Comparing blob data...
  Blob 0: ✓ identical (0x01ac7e2c7fff656a02bb7d8e9934798ab3d1df8fbf20acff5aec87b183fd99cf)
  Blob 1: ✓ identical (0x01808fa4fb38311c3a2a7c8a37d95af5a18eb3ccfe279d7e02f5df7d839b4a3a)
  Blob 2: ✓ identical (0x01e0b7530de207b244ce87448a633d7bb077339236d4a4e82985b944553913dc)

Performance comparison:
  Legacy endpoint: 2.242901587s
  New endpoint:    498.302806ms
  New endpoint is 77.8% faster

[github-actions]

✅ All tests successful. No failed tests were found.

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[joshuacolvin0]

LGTM