Add Debugf and some minor updates to timer queue processor base

[taylanisikdemir]

What changed?

• Some non-behavioral changes in timer queue processor:
  • add debug logs
  • reduce unnecessary multiline formatting
  • wrap too many return parameters in a struct
  • move handling logic to helper functions to make processing loop more lean/readable
• Introduce Debugf as a shortcut to logger.Debug(fmt.Sprintf(..)).
• Use zaplogger's Check() to avoid processing log tags for Debug logs. Since we plan to add more verbose logs this can help reduce GC overhead in prod.

Misc. change:

• Added 30s sleep before running unit test CI job as workaround to failing make install-schema due to Cassandra not ready.

Why?
Improve debugging

How did you test it?
make test