feat: exit immediately when stacks-node block desync detected

[zone117x]

(Note: for now, this is primarily a testing PR for debugging desync issues)

This PR changes the behavior for when the API encounters a "desync" error with the stacks-node (event emitter). A desync being: when the stacks-node emits a /new_block event containing a pointer to a parent block that the API has not received from any previous /new_block events. Typically this happens when some out-of-order or buggy shutdown sequence occurs between the API and stacks-node.

The API is unable to handle re-orgs and serve data in a "lossy" mode with missing blocks/txs. So prior to this PR, the API would return an http error response to the stacks-node, then the stacks-node would try to re-emit the same event, and this would just repeat indefinitely. This results in the db event_observer_requests table growing indefinitely, and a configured tsv output file growing indefinitely.

With this PR, when a desync occurs, the program exits immediately with a specific error message and exit code.

[github-actions[bot]]

🚀 Deployed on https://deploy-preview-973--stacks-blockchain-api.netlify.app

[codecov-commenter]

Codecov Report

Merging #973 (ee92ee4) into master (64a4401) will increase coverage by 0.04%. The diff coverage is 53.84%.

@@            Coverage Diff             @@
##           master     #973      +/-   ##
==========================================
+ Coverage   66.88%   66.93%   +0.04%     
==========================================
  Files          95       95              
  Lines       10036    10047      +11     
  Branches     1573     1624      +51     
==========================================
+ Hits         6713     6725      +12     
+ Misses       3319     3318       -1     
  Partials        4        4              

Impacted Files	Coverage Δ
src/datastore/postgres-store.ts	84.82% <33.33%> (-0.04%)	:arrow_down:
src/shutdown-handler.ts	18.96% <60.00%> (+18.96%)	:arrow_up:

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[smcclellan]

@zone117x This seems abandoned -- any reason not to close?