feat(proxyd): track consensus for {safe,finalized} blocks and rewrite tags

[felipe-op]

Description

This change adds the ability to track finalized and safe block tags within a backend group. It uses the same consensus poller mechanism, and converge to the lowest block.

Those tags are not used to form a consensus, only to maintain a consistent view from client perspective.

It shallowly check the values for sanity, i.e. tag values should never decrease, and finalized <= safe <= latest. In case of an unexpected scenario, we ban the backend and try to re-establish the consensus. If all backends are observing the same reorg, all of them will be banned and we'll stop serving traffic temporarily.

Note this is a very rare event and we are trying to prevent overreacting to a bad node.

Re-establishing the consensus may result in safe or finalized to drop in the same way a backend would do if such reorg would be observed.

Tests

Added tests to cover new cases

Invariants

• bumped go to 1.20
• refactored tests
• refactored poller
• adjusted the max block lag to saner default of 8

Additional context

This is part of the project Consensus Aware RPC Proxy: https://www.notion.so/oplabs/Consensus-Aware-RPC-Proxy-0138e029af814e4cbca2740c7888e02d

Metadata

https://linear.app/optimism/issue/INF-246/add-safe-and-finalized-blocks-to-consensus-proxyd

TODOs

• Author or reviewer has added an entry to the current release notes draft, if appropriate. -- not applicable

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[codecov]

Codecov Report

Merging #5794 (dad7aee) into develop (a680097) will decrease coverage by 2.57%.
The diff coverage is n/a.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #5794      +/-   ##
===========================================
- Coverage    42.27%   39.70%   -2.57%     
===========================================
  Files          464      306     -158     
  Lines        30078    25417    -4661     
  Branches       876        0     -876     
===========================================
- Hits         12714    10091    -2623     
+ Misses       16362    14372    -1990     
+ Partials      1002      954      -48     

Flag	Coverage Δ
bedrock-go-tests	39.70% <ø> (+<0.01%)	⬆️
common-ts-tests	?
contracts-bedrock-tests	?
contracts-tests	?
core-utils-tests	?
dtl-tests	?
fault-detector-tests	?
sdk-tests	?

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