Log exceptions in Commits::CreateService

If an exception is caught in Commits::CreateService, the return value is handled by the caller, but there is currently no way for an admin to know what happened because there are many possibilities (e.g. validation error, pre-receive error, etc.).

For better observability, this change logs the exception but does not report it to Sentry because that could create noise (e.g. repository size limits exceeded is not a bug in the system).

Relates to #220168 (closed)