Update-only engine listener and atomic config handling

[Anilm3]

Description

• Make config aggregators atomic, i.e. a configuration with an error does not result in any changes.
• Update engine listener to avoid affecting products without updates, removals or new configs.

Motivation

Additional Notes

Describe how to test your changes

Readiness checklist

• Unit tests have been updated and pass
• If known, an appropriate milestone has been selected
• All new source files include the required notice

Release checklist

• The CHANGELOG.md has been updated

[codecov-commenter]

Codecov Report

Merging #253 (aa3b45d) into master (f9fb3c7) will decrease coverage by 10.64%.
The diff coverage is 43.18%.

@@             Coverage Diff             @@
##           master     #253       +/-   ##
===========================================
- Coverage   63.83%   53.19%   -10.64%     
===========================================
  Files          94       69       -25     
  Lines        5660     2455     -3205     
  Branches     1808     1108      -700     
===========================================
- Hits         3613     1306     -2307     
+ Misses        984      436      -548     
+ Partials     1063      713      -350     

Flag	Coverage Δ
extension	?
helper	53.19% <43.18%> (-0.19%)	⬇️

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Impacted Files	Coverage Δ
...ig/listeners/config_aggregators/asm_aggregator.hpp	66.66% <0.00%> (ø)
...steners/config_aggregators/asm_data_aggregator.hpp	83.33% <0.00%> (ø)
...helper/remote_config/listeners/engine_listener.hpp	66.66% <ø> (ø)
...listeners/config_aggregators/asm_dd_aggregator.cpp	31.57% <18.18%> (-14.58%)	⬇️
...helper/remote_config/listeners/engine_listener.cpp	50.00% <31.57%> (-6.25%)	⬇️
...ig/listeners/config_aggregators/asm_aggregator.cpp	50.00% <38.88%> (-2.00%)	⬇️
...steners/config_aggregators/asm_data_aggregator.cpp	54.08% <60.52%> (+1.85%)	⬆️

... and 25 files with indirect coverage changes

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