fix: Properly catch cronjob errors during initialization

[FrederikBolding]

This PR fixes two issues:

Firstly, we were not catching errors thrown during the "daily checkin" of the CronjobController, this means that if one Snap failed we would not complete the initialization of the controller and no cronjobs would run.

Secondly, we were running all the cronjobs sequentially during "daily check" which seems unintentional given that we don't need the result of the cronjob invocation.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.06%. Comparing base (d87cf44) to head (a5c5244).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3373      +/-   ##
==========================================
+ Coverage   98.03%   98.06%   +0.02%     
==========================================
  Files         397      397              
  Lines       10899    10898       -1     
  Branches     1714     1714              
==========================================
+ Hits        10685    10687       +2     
+ Misses        214      211       -3     

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