Add opt-in tracing for periodic log uploads

Based on a customer feedback, we found there are cases that logs stopped being updated to metaflow cli console display, while the mflog inside the execution container are updated correctly. We speculate there are issues with the log updating sidecar (SaveLogsPeriodicallySidecar). However we don't have enough instrumentation on the sidecar itself.

We propose this issue to add tracing for the sidecar itself.