Engine API: make engine_getPayloadVN fork agnostic (#355)

* Engine API: make engine_getPayloadVN fork agnostic

* Fix links

Author: ethDreamer

src/engine/experimental/blob-extension.md

@@ -92,7 +92,10 @@ Refer to the response for `engine_newPayloadV2`.
 #### Response
 
 * result: `object`
-  - `executionPayload`: [`ExecutionPayloadV3`](#ExecutionPayloadV3)
+  - `executionPayload`: [`ExecutionPayloadV1`](../paris.md#ExecutionPayloadV1) | [`ExecutionPayloadV2`](../shanghai.md#ExecutionPayloadV2) |  [`ExecutionPayloadV3`](#ExecutionPayloadV3) where:
+    - `ExecutionPayloadV1` **MUST** be returned if the payload `timestamp` is lower than the Shanghai timestamp
+    - `ExecutionPayloadV2` **MUST** be returned if the payload `timestamp` is greater or equal to the Shanghai timestamp and lower than the EIP-4844 activation timestamp
+    - `ExecutionPayloadV3` **MUST** be returned if the payload `timestamp` is greater or equal to the EIP-4844 activation timestamp
   - `blockValue` : `QUANTITY`, 256 Bits - The expected value to be received by the `feeRecipient` in wei
 * error: code and message set in case an exception happens while getting the payload.
 

src/engine/shanghai.md

@@ -135,7 +135,9 @@ This method follows the same specification as [`engine_forkchoiceUpdatedV1`](./p
 #### Response
 
 * result: `object`
-  - `executionPayload`: [`ExecutionPayloadV2`](#ExecutionPayloadV2)
+  - `executionPayload`: [`ExecutionPayloadV1`](./paris.md#ExecutionPayloadV1) | [`ExecutionPayloadV2`](#ExecutionPayloadV2) where:
+      - `ExecutionPayloadV1` **MUST** be returned if the payload `timestamp` is lower than the Shanghai timestamp
+      - `ExecutionPayloadV2` **MUST** be returned if the payload `timestamp` is greater or equal to the Shanghai timestamp
   - `blockValue` : `QUANTITY`, 256 Bits - The expected value to be received by the `feeRecipient` in wei
 * error: code and message set in case an exception happens while getting the payload.