pysmurf-controller: Add fields to session.data to track when stream is enabled

[BrianJKoopman]

Description

This PR adds the 'stream_on' and 'last_updated' fields to session.data within the stream process. It also adds a log message recording the duration of this initialization process.

Reviewers

@kmharrington, lemme know if that logging is sufficient for what you want. @msilvafe and @tristpinsm, just wanted to keep you aware of changes.

Motivation and Context

This will enable an OCSClient to check whether or not the stream is on, and whether 'stream_on' is a recent value. This will be used downstream when addressing simonsobs/sorunlib#215.

The initialization timer will help identify how long this startup is actually taking. We know its ~30 seconds. However, it won't break down which components are slowest. Thoughts related to that are welcome.

Resolves #897.

How Has This Been Tested?

This has not been tested, but they are relatively innocuous changes.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.