Add better error handling for ConfigSnapshotServiceProvider::register

Thanks for working on this @trackleft2 !
Tested out a few aspects of this:

Verified that services are still being registered:

$ drush devel:services
...
- config_snapshot.config_sync.module.pathauto
- config_snapshot.config_sync.module.redirect
- config_snapshot.config_sync.module.search
- config_snapshot.config_sync.module.shortcut
...

Verified that errors are logged if unhandled exceptions occur elsewhere in provisioning the storage:

Error initializing config storage: Failed to retrieve config storage.
(And - separate error forced):
Error initializing config storage: An unrelated error somewhere else occurred.

Verified that errors are logged in the case of any of snapshotSet, extensionType, and extensionName being absent from malformed snapshots (in separate cases):

Error processing config ID config_snapshot.snapshot..module.search: Invalid snapshot data for config ID config_snapshot.snapshot..module.search
Error processing config ID config_snapshot.snapshot.config_sync..search: Invalid snapshot data for config ID config_snapshot.snapshot.config_sync..search
Error processing config ID config_snapshot.snapshot.config_sync.module.: Invalid snapshot data for config ID config_snapshot.snapshot.config_sync.module.

The only thing I noted was that the PHP error_log is used, rather than the Drupal log. But given that this is the service discovery phase, I'm not sure if using the Drupal log channel would even make sense. Perhaps that's why you selected the PHP error log to begin with?

Thanks all!

Automatically closed - issue fixed for 2 weeks with no activity.