CI integration test - run only once a day, report failures on IRC

[lslezak]

Problem

• We run the integration test for every single commit and pull request
• But it takes quite long time (6-10 minutes)
• And in reality it does not check much as there are just trivial tests which just verify that the Agama is up and running
• In most cases it just wastes resources and you need to wait longer to get a green check mark

Solution

• Use a scheduled run instead, run it once a day
• Start it at 10:50 so the possible failure is reported just before the daily call so the most developers are connected to the IRC at that time (the highest chance that somebody can see that message 😃)

Testing

• Tested manually in my fork with explicit build failure (exit 1), it reported this to IRC:

  <github-action> Agama integration test failed: https://github.com/lslezak/agama/actions/runs/6863503060
  <-- github-action (~ircbot@74.249.21.245) left the channel