fix: preserve hard-strict priority when the worker pool is busy

[0x0fee]

Description

When the shared worker pool is busy, HardStrictPriorityPoller temporarily skips queues with pending messages, allowing lower-priority work to run first. Limit temporary queue deactivation to NO_MESSAGE so pending high-priority work remains visible.

Type of change

• Bug fix

How Has This Been Tested?

• Unit tests

Added 2 unit tests:

1. A busy pool must not hide pending high-priority messages. This test fails before the fix and passes afterward.
2. Empty queues must still be temporarily skipped.

Result: all 22 selected priority tests pass, including the 2 new tests.

./gradlew :rqueue-core:test --tests '*HardStrictPriorityPoller*' --tests '*RqueueMessageListenerContainerPriorityTest' --tests '*PriorityGroupListenerTest'

Test configuration: JDK 17, Gradle 9.3.0.

Checklist

• Code reviewed and formatting checked
• 2 unit tests added; all 22 selected tests pass