Improve logging of add-ons pending install forcing a restart (#15892)
Relates to #15719
Summary of the issue:
When triaging #15719, important information from the log is missing.
The reporter is stuck with a pending restart dialog appearing every time they close the add-on store.
For reasons other than a pending install, the first add-on found to be modified is logged.
For pending installs, all add-ons pending an install should be logged.
Description of user facing changes
None
Description of development approach
Log all add-ons pending install when triggering the restart dialog