Solution for preserving service resource attributes in logs

[damemi]

#564 follows metrics' approach of copy service resource attributes to labels in the LogEntry by default.

This could ultimately cause problems if we hit the limit for labels on a LogEntry. Going forward, we should determine if this is a suitable place to store them, or if we want to consider other options (jsonPayload/other storage, etc)

[damemi]

cc @jsuereth

[aabmass]

No update here, but dropping to P3