Limit Edge query threads and remove unused binary allocator

[JackieTien97]

Description

Edge still creates query scheduling notifications through an unbounded cached pool, while fragment dispatch uses a hard-coded minimum of 20 workers. Add restart-only settings and set both Edge defaults to 2:

Setting	General default	Edge default
driver_task_scheduler_notification_thread_count	0: retain the existing unbounded cached pool	2
fragment_instance_dispatch_thread_count	0: use max(20, available processors × 2)	2

Positive notification sizes queue callbacks on a limited worker pool; workers can exit after 60 seconds of inactivity. Callbacks do not fall back to the threads completing driver futures. Fragment dispatch retains its existing caller-runs behavior when the pool is busy. Negative configuration values are rejected.

Remove the unused BinaryAllocator implementation, its configuration, metrics and lifecycle hooks. Repository-wide call-site inspection found allocation/deallocation calls only in its unit tests; production references merely started it through GC monitoring or configuration reload. The old auto-releaser could remain blocked in ReferenceQueue.remove() after shutdown, accumulating threads across restarts. Removing the unused subsystem prevents those workers from being created. Normal BLOB handling remains covered by the real Edge read/write test.

ConfigNode and SchemaRegion continue to use Ratis; DataRegion continues to use IoTConsensus.

Validation

Validated after rebasing onto master (4f2eb0c790):

• Clean distribution build; all six distribution artifacts produced. The packaged node-commons jar contains no binaryallocator classes.
• Four unit tests passed: configuration defaults/validation/startup/restart-only behavior, driver scheduling, and 12 blocked-driver notifications completing through two workers without executing on the completing thread.
• Seven IoTDBEdgeBasicIT tests passed, including tree/table reads and writes, concurrent table queries, 40 cross-database join queries across four concurrent connections, consensus assertions, and a 64 KiB BLOB verified before/after flush and configuration reload.
• Edge starts and reloads a configuration retaining the legacy enable_binary_allocator=true key. The thread dumps contain no BinaryAllocator workers. The cross-database join dump contains two fragment-dispatch workers and two driver-notification workers.
• Full-reactor English and Chinese test compilation passed.