fix(toolkit-lib): log monitor error missing from IoMessage

[mrgrain]

Fixes the error messages not being include for generic LogMonitor errors.
Also updates the tests to be more reliable.

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.15%. Comparing base (cf68e32) to head (a72f7db).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #438   +/-   ##
=======================================
  Coverage   79.15%   79.15%           
=======================================
  Files          54       54           
  Lines        6889     6889           
  Branches      773      772    -1     
=======================================
  Hits         5453     5453           
  Misses       1418     1418           
  Partials       18       18           

Flag	Coverage Δ
suite.unit	79.15% <ø> (ø)

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