Remove DistributedSemaphores functionality

[stidsborg]

Summary

• Removes the DistributedSemaphores / DistributedSemaphore API and its Synchronization wrapper, along with ExistingSemaphores, SemaphoreStatus, and SemaphoreIdAndStatus
• Drops ISemaphoreStore plus the in-memory, PostgreSQL, SQL Server, and MariaDB implementations (no more *_semaphores table on init/truncate)
• Strips wiring from Workflow, Invoker, InvocationHelper, ControlPanel/ControlPanelFactory, IFunctionStore, and the CrashableFunctionStore test/sample wrappers; deletes the Subscription and BankTransfer/Locking samples that only existed to demo the lock API
• AsyncSemaphore (the in-process parallelism limiter used by PostponedWatchdog) is unrelated and kept

Test plan

• dotnet build Cleipnir.ResilientFunctions.sln — 0 warnings, 0 errors
• dotnet test ./Core/Cleipnir.ResilientFunctions.Tests — 545/545 passing
• Run store-specific test suites (PostgreSQL / SQL Server / MariaDB) against Docker Compose
• Confirm existing deployments handle the leftover *_semaphores table (manual DROP TABLE if a clean schema is desired)