[core] Inconsistent timestamp handling

[rynewang]

What happened + What you expected to happen

gcs::CreateErrorTableData takes a double timestamp.

Here it takes milliseconds from std clock:

ray/src/ray/raylet/node_manager.cc

Line 2177 in d4e2660

gcs::CreateErrorTableData("task", error_message, current_time_ms(), job_id);

Here it takes nanoseconds from absl:

ray/src/ray/gcs/gcs_server/gcs_actor_manager.cc

Line 755 in d4e2660

absl::GetCurrentTimeNanos(),

We need to:

1. figure out it takes ms or ns
2. fix by changing arg to absl::Time

Versions / Dependencies

master

Reproduction script

Issue Severity

Medium: It is a significant difficulty but I can work around it.

[dentiny]

Reading through the initial PR (https://github.com/ray-project/ray/pull/2256/files), the unit is actually seconds.

[dentiny]

Then refactored to protobuf in #5024.