Add examples for engine methods

[alexandratran]

Add examples for:

• engine_exchangeCapabilities
• engine_exchangeTransitionConfigurationV1
• engine_forkchoiceUpdatedV1
• engine_forkchoiceUpdatedV2
• engine_forkchoiceUpdatedV3
• engine_getPayloadBodiesByHashV1
• engine_getPayloadBodiesByRangeV1
• engine_getPayloadV1
• engine_getPayloadV2
• engine_getPayloadV3
• engine_newPayloadV1
• engine_newPayloadV2
• engine_newPayloadV3

The V1 examples are taken from the Besu Engine API docs.

This will be one in a series of PRs adding examples to this OpenRPC spec.

[mkalinin]

This is great! I wish Engine API were getting these examples in its early days :-D

I understand that they are brought from Besu API docs and happy to merge this PR as is. But the following additions would be really nice:

• forkchoiceUpdated example with non-null payloadAttributes (can be assembled from forkchoiceUpdatedV1 and getPayloadV1 examples)
• newPayload example with INVALID payload status in the response
• V2 and V3 examples for each method

[mkalinin]

Spellchecker has a problem with hex strings. I have found the following solution to that:

  - name: json schemas
    ...
    pipeline:
    - pyspelling.filters.context:
        context_visible_first: true
        delimiters:
        - open: ''
          content: 0x[a-fA-F0-9]+
          close: ''

cc @lightclient

[alexandratran]

@mkalinin thanks for the feedback. I've made the additions as per your request, but I need some confirmation and additional input for some of the added examples. In particular, can you provide good examples for the following parameters?

• engine_newPayloadV3: blobGasUsed, excessBlobGas, and expected blob versioned hashes
• engine_getPayloadV3: blobsBundle object

[mkalinin]

I think you can find good examples of these methods calls in the Hive logs, for instance, here is the Besu logs of Cancun Engine API checks.

[alexandratran]

@mkalinin Thanks, added in the missing examples.

[mkalinin]

Blobs are huge! Maybe we want to trim its values, curious what others think about it? cc @lightclient

[mkalinin]

Great work! thank you!

[alexandratran]

@mkalinin Thanks! When ready, can you merge this (since I don't have write access)? Also, I have a similar PR open adding debug examples: #464.