Backport asynchronous write backpressure to 3.4

[jcalcote]

Backport of #120 to the 3.4 release branch for the planned 3.4.4 release.

Changes

• Stop accepting new streaming writes once the Grizzly asynchronous write queue is full.
• Release the rejected buffer and terminate the saturated connection with an EOF-style failure.
• Notify an application callback of write failure only while its request remains pending in ReplyQueue, preventing timeout-plus-write-failure double completion and detaching timed-out callbacks from queued writes.
• Add regression tests for queue saturation and timeout-before-write-failure ordering.

Validation

• JAVA_HOME=/usr/lib/jvm/java-21-openjdk-21.0.5.0.10-3.el8.x86_64 mvn --batch-mode --update-snapshots clean package
• All six modules passed on the 3.4.4-SNAPSHOT branch.
• 168 tests passed with 2 existing skips.
• Compiled classes are Java 17 bytecode (major version 61).
• git diff --check passed.

Related issue: #119.