[Merge] Implement execution_layer (#2635)

* Checkout serde_utils from rayonism

* Make eth1::http functions pub

* Add bones of execution_layer

* Modify decoding

* Expose Transaction, cargo fmt

* Add executePayload

* Add all minimal spec endpoints

* Start adding json rpc wrapper

* Finish custom JSON response handler

* Switch to new rpc sending method

* Add first test

* Fix camelCase

* Finish adding tests

* Begin threading execution layer into BeaconChain

* Fix clippy lints

* Fix clippy lints

* Thread execution layer into ClientBuilder

* Add CLI flags

* Add block processing methods to ExecutionLayer

* Add block_on to execution_layer

* Integrate execute_payload

* Add extra_data field

* Begin implementing payload handle

* Send consensus valid/invalid messages

* Fix minor type in task_executor

* Call forkchoiceUpdated

* Add search for TTD block

* Thread TTD into execution layer

* Allow producing block with execution payload

* Add LRU cache for execution blocks

* Remove duplicate 0x on ssz_types serialization

* Add tests for block getter methods

* Add basic block generator impl

* Add is_valid_terminal_block to EL

* Verify merge block in block_verification

* Partially implement --terminal-block-hash-override

* Add terminal_block_hash to ChainSpec

* Remove Option from terminal_block_hash in EL

* Revert merge changes to consensus/fork_choice

* Remove commented-out code

* Add bones for handling RPC methods on test server

* Add first ExecutionLayer tests

* Add testing for finding terminal block

* Prevent infinite loops

* Add insert_merge_block to block gen

* Add block gen test for pos blocks

* Start adding payloads to block gen

* Fix clippy lints

* Add execution payload to block gen

* Add execute_payload to block_gen

* Refactor block gen

* Add all routes to mock server

* Use Uint256 for base_fee_per_gas

* Add working execution chain build

* Remove unused var

* Revert "Use Uint256 for base_fee_per_gas"

This reverts commit 6c88f19ac4.

* Fix base_fee_for_gas Uint256

* Update execute payload handle

* Improve testing, fix bugs

* Fix default fee-recipient

* Fix fee-recipient address (again)

* Add check for terminal block, add comments, tidy

* Apply suggestions from code review

Co-authored-by: realbigsean <seananderson33@GMAIL.com>

* Fix is_none on handle Drop

* Remove commented-out tests

Co-authored-by: realbigsean <seananderson33@GMAIL.com>

beacon_node/src/cli.rs

@@ -371,6 +371,60 @@ pub fn cli_app<'a, 'b>() -> App<'a, 'b> {
                 .help("Specifies how many blocks the database should cache in memory [default: 5]")
                 .takes_value(true)
         )
+        /*
+         * Execution Layer Integration
+         */
+        .arg(
+            Arg::with_name("merge")
+                .long("merge")
+                .help("Enable the features necessary to run merge testnets. This feature \
+                       is unstable and is for developers only.")
+                .takes_value(false),
+        )
+        .arg(
+            Arg::with_name("execution-endpoints")
+                .long("execution-endpoints")
+                .value_name("EXECUTION-ENDPOINTS")
+                .help("One or more comma-delimited server endpoints for HTTP JSON-RPC connection. \
+                       If multiple endpoints are given the endpoints are used as fallback in the \
+                       given order. Also enables the --merge flag. \
+                       If this flag is omitted and the --eth1-endpoints is supplied, those values \
+                       will be used. Defaults to http://127.0.0.1:8545.")
+                .takes_value(true)
+        )
+        .arg(
+            Arg::with_name("terminal-total-difficulty-override")
+                .long("terminal-total-difficulty-override")
+                .value_name("TERMINAL_TOTAL_DIFFICULTY")
+                .help("Used to coordinate manual overrides to the TERMINAL_TOTAL_DIFFICULTY parameter. \
+                       This flag should only be used if the user has a clear understanding that \
+                       the broad Ethereum community has elected to override the terminal difficulty. \
+                       Incorrect use of this flag will cause your node to experience a consensus
+                       failure. Be extremely careful with this flag.")
+                .takes_value(true)
+        )
+        .arg(
+            Arg::with_name("terminal-block-hash-override")
+                .long("terminal-block-hash-override")
+                .value_name("TERMINAL_BLOCK_HASH")
+                .help("Used to coordinate manual overrides to the TERMINAL_BLOCK_HASH parameter. \
+                       This flag should only be used if the user has a clear understanding that \
+                       the broad Ethereum community has elected to override the terminal PoW block. \
+                       Incorrect use of this flag will cause your node to experience a consensus
+                       failure. Be extremely careful with this flag.")
+                .takes_value(true)
+        )
+        .arg(
+            Arg::with_name("fee-recipient")
+                .long("fee-recipient")
+                .help("Once the merge has happened, this address will receive transaction fees \
+                       collected from any blocks produced by this node. Defaults to a junk \
+                       address whilst the merge is in development stages. THE DEFAULT VALUE \
+                       WILL BE REMOVED BEFORE THE MERGE ENTERS PRODUCTION")
+                // TODO: remove this default value. It's just there to make life easy during merge
+                // testnets.
+                .default_value("0x0000000000000000000000000000000000000001"),
+        )
 
         /*
          * Database purging and compaction.