Added new API endpoints (logs, evidence)

[jleaniz]

Description of the change

This PR creates new API endpoints to retrieve log data for Turbinia components in a similar way to the "tail" command.

It also adds a new endpoint to download evidence files based on evidence IDs.

Applicable issues

• fixes #1528

Additional information

Checklist

• [X] All tests were successful.
• [X] Unit tests added.
• [X] Documentation updated.

[jleaniz]