Reduce subscriber contention with bounded spinning

[prezaei]

When subscribers contend for the read lock, blocking Dequeue currently yields and progresses to semaphore waits of up to 10 ms. Use bounded SpinWait retries before a 5 ms semaphore wait, resetting the spin budget after waiting. TryDequeue still makes one read-lock attempt, and the existing publisher/subscriber crash recovery remains intact. Also observe cancellation while waiting for a publisher to finish writing a reserved message.

Add eight regression cases covering contended reads, expired read locks, cancellation, and exactly-once delivery with concurrent publishers and subscribers. Add a reproducible concurrent-subscriber benchmark, support benchmark selection from the command line, and update existing benchmark jobs to .NET 10. This branch includes current main and the queue lifetime fix.

Validation:

• macOS and Linux full suites: 101 passed, 3 platform-specific skips each.
• Release solution build: zero warnings or errors.
• CI passed on Windows, macOS, and Linux for commit 03ef4d8: https://github.com/cloudtoid/interprocess/actions/runs/34725696901

BenchmarkDotNet comparison against main, with one publisher sending batches of 65,536 eight-byte messages. Values are mean time per message; lower is better.

Environment	Subscribers	main	This PR
Linux arm64 container, .NET 10	1	134.6 ns	135.8 ns
Linux arm64 container, .NET 10	4	546.5 ns	199.7 ns
macOS M5 Max, .NET 10	1	253.3 ns	241.0 ns
macOS M5 Max, .NET 10	4	1,505.4 ns	342.0 ns

Linux used three warmup and eight measured iterations; macOS used three of each. These are local measurements, not general latency guarantees; the macOS contended baseline was noisy. Linux shows about 2.7x throughput with four subscribers and essentially unchanged single-subscriber throughput.

Reproduce from the repository root:

dotnet run --project src/Interprocess.Benchmark -c Release -- --filter '*SubscriberBenchmark*' --iterationCount 8