add activity_paused flag to ByID heartbeat response (#517)

<!-- Describe what has changed in this PR -->
**What changed?**
Add "activity_paused" flag to RecordActivityTaskHeartbeatByIdResponse.

<!-- Tell your future self why have you made these changes -->
**Why?**
1. It is needed to let long-running activity know that activity was
paused on the server.
2. Because it is missing in RecordActivityTaskHeartbeatByIdResponse but
present in RecordActivityTaskHeartbeatResponse

<!-- Are there any breaking changes on binary or code level? -->
**Breaking changes**
No.

Author: ychebotarev