Check verified session first while choosing the result from multiple untrusted sessions

[leszko]

What does this pull request do? Explain your changes. (required)
When there are multiple untrusted sessions (orchestrators), then check first the result from the verified session. This is one of the changes that will prevent bouncing between different orchestrators while transcoding a stream.

related to #2097

Note: This change alone does not completely prevent bouncing between different sessions. Swapping sessions also occur here.

Specific updates (required)

• Refactor broadcast.go: extract collectResults() function to make it testable
• Add unit test for collectResults()
• Make verified session returned first from collectResults()

How did you test each of these updates (required)

1. Add printing the currently verified session and the result session
2. Build the project
3. Run the local setup with 1 trusted orchestrator and 3 untrusted orchestrator
4. Check that the currently verified session is always the one selected from multiple results

Does this pull request close any open issues?

Checklist:

• Read the contribution guide
• make runs successfully
• All tests in ./test.sh pass
• README and other documentation updated
• Pending changelog updated

[darkdarkdragon]

LGTM!

[jailuthra]

LGTM 🚢

[yondonfu]

LGTM!