Add support for UpsertSearchAttributes to describe in the test service

[nagl-stripe]

What was changed

This makes the implementation of DescribeWorkflowExecution in the test service aware of calls to Workflow.upsertSearchAttributes.

Why?

The test service's describe method had a bug that impacted any workflow that upserted search attributes.

Checklist

1. Closes (nothing)

2. How was this tested:

cd temporal-sdk
# using TestWorkflowService
USE_DOCKER_SERVICE=false ../gradlew test --tests io.temporal.workflow.DescribeTest
# using docker-compose to make sure we match the real service's behavior
USE_DOCKER_SERVICE=true ../gradlew test --tests io.temporal.workflow.DescribeTest

3. Any docs updates needed?
   None.

[Spikhalskiy]

Thank you for the contribution, great job!