fix(ps): mark streaming sub active before opening grpc stream

[sicoyle]

Description

Fixes a race in the sync streaming Subscription that made test_streaming_subscribe_receives_published_message fail intermittently in CI. The same race can drop real user subscriptions on connect.

Subscription.start() created the bidi stream and only then marked it active. gRPC starts reading the request iterator on its own thread before SubscribeTopicEventsAlpha1() returns. When that thread won the race, the iterator sent the initial request, saw the stream as inactive, and ended. That half-closed the stream, so the sidecar unsubscribed right away and the client got UNKNOWN: EOF. The reconnect hit the same race, next_message() returned None, and the test failed with 'NoneType' object has no attribute 'data'.

The async Subscription is not affected, since it marks the stream active before its first await.

Changes

• dapr/clients/grpc/subscription.py: mark the stream active before creating it, and mark it inactive again if setup fails.
• dapr/clients/grpc/subscription.py: give each stream its own send queue, and wait on it with a timeout. Before this, an iterator left over after close() or a reconnect blocked forever on a shared queue and could take acks meant for the new stream.
• tests/clients/test_subscription.py: add unit tests with a stub that reads the request iterator before start() returns, which reproduces the race every time. Also check that the iterator exits after close().
• tests/integration/test_pubsub.py: keep reading when next_message() returns None, since the API documents that as the normal result of a reconnect.

Testing

• The new unit test fails on master and passes with this fix.
• The full unit suite, ruff and mypy pass.
• The integration tests run in CI against a real sidecar.

Issue reference

We strive to have all PR being opened based on an issue, where the problem or feature have been discussed prior to implementation.

Please reference the issue this PR will close: #[issue number]

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly
• Created/updated tests
• Extended the documentation

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.91%. Comparing base (bffb749) to head (d6bb874).
⚠️ Report is 227 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1234      +/-   ##
==========================================
- Coverage   86.63%   83.91%   -2.72%     
==========================================
  Files          84      123      +39     
  Lines        4473    10260    +5787     
==========================================
+ Hits         3875     8610    +4735     
- Misses        598     1650    +1052     

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