Revert alerts, refactor docker image builds

[aaronchongth]

What's new

Supercedes #1060

• add alerts implementation back
• fix ci builds to no longer build messages from source
• update CI for different ros distros to check out to the respective branch
• bump codecov and other misc fixes to ci

Self-checks

• I'm familiar with and follow this Typescript guideline
• I added unit-tests for new components
• I tried testing edge cases
• I tested the behavior of the components that interact with the backend, with an e2e test

Discussion

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (main@7aa2653). Learn more about missing BASE report.
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1066   +/-   ##
=======================================
  Coverage        ?   70.00%           
=======================================
  Files           ?      288           
  Lines           ?    14173           
  Branches        ?     1136           
=======================================
  Hits            ?     9922           
  Misses          ?     4227           
  Partials        ?       24           

Flag	Coverage Δ
api-server	79.39% <100.00%> (?)
rmf-dashboard-framework	67.41% <ø> (?)

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