HandleEvidence: Make logging message more human-readable

[lebogg]

Describe the bug Currently, the log message of handleEvidence is, e.g.: INFO[0010] Evaluating evidence 1 (1) collected by 1 at seconds:1645574399 nanos:999999999

To Reproduce Run engine and assess an evidence.

Expected behavior A human readable message, e.g.: INFO[0010] Evaluating evidence with ID: 1 (Resource ID: 1) collected by Tool 1 at 2022-02-22 23:59:59.999999999 or INFO[0010] Evaluating evidence (Evidence ID: 1 | Resource ID: 1 | Tool ID: 1 | Time: 2022-02-22 23:59:59.999999999)

Additional context Use Timestamp.AsTime() of the timestamppb package