Use blocks v3 endpoint in the VC (#4813)

* block v3 endpoint init

* block v3 flow

* block v3 flow

* continue refactor

* the full flow...

* add api logic

* add api logic

* add new endpoint version

* added v3 endpoint

* some debugging

* merge v2 flow with v3

* debugging

* tests passing

* tests passing

* revert cargo lock

* initial v3 test

* blinded payload test case passing

* fix clippy issues

* cleanup

* cleanup

* remove dead code

* fixed logs

* add block value

* block value fix

* linting

* merge unstable

* refactor

* add consensus block value

* lint

* update header name to consensus block value

* prevent setting the participation flag

* clone get_epoch_participation result

* fmt

* clone epoch participation outside of the loop

* add block v3 to vc

* add v3 logic into vc

* add produce-block-v3

* refactor based on feedback

* update

* remove comments

* refactor

* header bugfix

* fmt

* resolve merge conflicts

* fix merge

* fix merge

* refactor

* refactor

* cleanup

* lint

* changes based on feedback

* revert

* remove block v3 fallback to v2

* publish_block_v3 should return irrecoveerable errors

* comments

* comments

* fixed issues from merge

* merge conflicts

* Don't activate at fork; support builder_proposals

* Update CLI flags & book

* Remove duplicate `current_slot` parameter in `publish_block` function, and remove unnecessary clone.

* Revert changes on making block errors irrecoverable.

---------

Co-authored-by: Michael Sproul <michael@sigmaprime.io>
Co-authored-by: Jimmy Chen <jchen.tc@gmail.com>

validator_client/src/cli.rs

@@ -136,6 +136,15 @@ pub fn cli_app<'a, 'b>() -> App<'a, 'b> {
                 .value_name("FEE-RECIPIENT")
                 .takes_value(true)
         )
+        .arg(
+            Arg::with_name("produce-block-v3")
+                .long("produce-block-v3")
+                .help("Enable block production via the block v3 endpoint for this validator client. \
+                       This should only be enabled when paired with a beacon node \
+                       that has this endpoint implemented. This flag will be enabled by default in \
+                       future.")
+                .takes_value(false)
+        )
         /* REST API related arguments */
         .arg(
             Arg::with_name("http")