Generalize silence_polling to silence_queries

[diogovernier]

Closes #210. Supersedes #389.

Summary

Implements the silence_queries approach approved by @rosa in #198: a single unified config that silences all of Solid Queue's internal SQL logging, including polling, heartbeats, concurrency maintenance, process pruning, and scheduler dynamic task reloading.

silence_polling is preserved as a backward-compatible alias, as suggested by @namolnad in #210.

Motivation

silence_polling only covers worker and dispatcher polling queries. In practice, heartbeat UPDATEs (every 60s per process), semaphore expiration, blocked execution unblocking, and dead process pruning are equally noisy, especially in development or when running with RAILS_LOG_LEVEL=debug.

Multiple users have reported this (#210, #389 comments, workarounds via custom log-level overrides and monkeypatches), and @rosa indicated in #389 that she'd prefer a single unified toggle over accumulating per-feature silencing flags:

"I was hoping we could get #210 done instead of having a bunch of different options to silence different parts."

Approach

• Extracts a shared with_silenced_queries helper in AppExecutor (which is already included by every class that touches the DB)
• Poller#with_polling_volume now delegates to the shared helper instead of inlining the silencing logic
• All periodic internal operations are wrapped: heartbeats, concurrency maintenance, process pruning, scheduler dynamic task reloading, and metadata reload
• One-time boot queries (e.g., schedule_tasks, fail_orphaned_executions) are deliberately not silenced. They can be useful for debugging deployment issues and only run once

What changed

File	Change
lib/solid_queue.rb	mattr_accessor :silence_queries replaces :silence_polling; backward-compat alias methods added
lib/solid_queue/app_executor.rb	New with_silenced_queries helper (shared by all call sites)
lib/solid_queue/processes/poller.rb	with_polling_volume now delegates to with_silenced_queries
lib/solid_queue/processes/registrable.rb	Heartbeat timer and reload_metadata wrapped
lib/solid_queue/dispatcher/concurrency_maintenance.rb	expire_semaphores and unblock_blocked_executions wrapped
lib/solid_queue/supervisor/maintenance.rb	prune_dead_processes wrapped
lib/solid_queue/scheduler/recurring_schedule.rb	reschedule_dynamic_tasks wrapped
README.md	Docs updated to reference silence_queries; mentions silence_polling alias
test/unit/worker_test.rb	Existing polling tests updated + new heartbeat silencing tests + backward-compat test
test/unit/dispatcher_test.rb	Existing polling tests updated to use new config name

Backward compatibility

Existing config.solid_queue.silence_polling = true/false continues to work. The engine initializer calls SolidQueue.public_send("silence_polling=", value), which hits our custom setter and delegates to silence_queries=. Getter and predicate methods also delegate. No breaking changes.