* adds ValidateBlock request to state
* adds `Request` enum in block verifier
skips solution check for BlockProposal requests
calls CheckBlockValidity instead of Commit block for BlockProposal requests
* uses new Request in references to chain verifier
* adds getblocktemplate proposal mode response type
* makes getblocktemplate-rpcs feature in zebra-consensus select getblocktemplate-rpcs in zebra-state
* Adds PR review revisions
* adds info log in CheckBlockProposalValidity
* Reverts replacement of match statement
* adds `GetBlockTemplate::capabilities` fn
* conditions calling checkpoint verifier on !request.is_proposal
* updates references to validate_and_commit_non_finalized
* adds snapshot test, updates test vectors
* adds `should_count_metrics` to NonFinalizedState
* Returns an error from chain verifier for block proposal requests below checkpoint height
adds feature flags
* adds "proposal" to GET_BLOCK_TEMPLATE_CAPABILITIES_FIELD
* adds back block::Request to zebra-consensus lib
* updates snapshots
* Removes unnecessary network arg
* skips req in tracing intstrument for read state
* Moves out block proposal validation to its own fn
* corrects `difficulty_threshold_is_valid` docs
adds/fixes some comments, adds TODOs
general cleanup from a self-review.
* Update zebra-state/src/service.rs
* Apply suggestions from code review
Co-authored-by: teor <teor@riseup.net>
* Update zebra-rpc/src/methods/get_block_template_rpcs.rs
Co-authored-by: teor <teor@riseup.net>
* check best chain tip
* Update zebra-state/src/service.rs
Co-authored-by: teor <teor@riseup.net>
* Applies cleanup suggestions from code review
Co-authored-by: teor <teor@riseup.net>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>