feat: improve scraper startup error handling

[kamiyaa]

Description

• handle errors and sets set chain metrics if scraper fails for chain during startup

Drive-by changes

• implement Clone for ScraperDb
  • this is because DbConn doesn't implement Clone when mock feature is enabled

Related issues

Fixes https://github.com/hyperlane-xyz/issues/issues/1408

Backward compatibility

Yes

Testing

Added unittest to test function. But don't have tests in place for testing the logic in Scraper::run()

[changeset-bot]

⚠️ No Changeset found

Latest commit: 94d1f9d

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.53%. Comparing base (9eb19ca) to head (94d1f9d).
Report is 21 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5191   +/-   ##
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  Coverage   77.53%   77.53%           
=======================================
  Files         103      103           
  Lines        2110     2110           
  Branches      190      190           
=======================================
  Hits         1636     1636           
  Misses        453      453           
  Partials       21       21           

Components	Coverage Δ
core	87.80% <ø> (ø)
hooks	79.39% <ø> (ø)
isms	83.68% <ø> (ø)
token	91.27% <ø> (ø)
middlewares	79.80% <ø> (ø)