chore: remove ~50k lines of unreachable dead code (#8913)

* chore: remove unreachable dead code across the codebase

Remove ~50,000 lines of unreachable code identified by static analysis.

Major removals:
- weed/filer/redis_lua: entire unused Redis Lua filer store implementation
- weed/wdclient/net2, resource_pool: unused connection/resource pool packages
- weed/plugin/worker/lifecycle: unused lifecycle plugin worker
- weed/s3api: unused S3 policy templates, presigned URL IAM, streaming copy,
  multipart IAM, key rotation, and various SSE helper functions
- weed/mq/kafka: unused partition mapping, compression, schema, and protocol functions
- weed/mq/offset: unused SQL storage and migration code
- weed/worker: unused registry, task, and monitoring functions
- weed/query: unused SQL engine, parquet scanner, and type functions
- weed/shell: unused EC proportional rebalance functions
- weed/storage/erasure_coding/distribution: unused distribution analysis functions
- Individual unreachable functions removed from 150+ files across admin,
  credential, filer, iam, kms, mount, mq, operation, pb, s3api, server,
  shell, storage, topology, and util packages

* fix(s3): reset shared memory store in IAM test to prevent flaky failure

TestLoadIAMManagerFromConfig_EmptyConfigWithFallbackKey was flaky because
the MemoryStore credential backend is a singleton registered via init().
Earlier tests that create anonymous identities pollute the shared store,
causing LookupAnonymous() to unexpectedly return true.

Fix by calling Reset() on the memory store before the test runs.

* style: run gofmt on changed files

* fix: restore KMS functions used by integration tests

* fix(plugin): prevent panic on send to closed worker session channel

The Plugin.sendToWorker method could panic with "send on closed channel"
when a worker disconnected while a message was being sent. The race was
between streamSession.close() closing the outgoing channel and sendToWorker
writing to it concurrently.

Add a done channel to streamSession that is closed before the outgoing
channel, and check it in sendToWorker's select to safely detect closed
sessions without panicking.

weed/worker/tasks/registry.go

@@ -64,51 +64,6 @@ func AutoRegisterUI(registerFunc func(*types.UIRegistry)) {
 	glog.V(1).Infof("Auto-registered task UI provider")
 }
 
-// SetDefaultCapabilitiesFromRegistry sets the default worker capabilities
-// based on all registered task types
-func SetDefaultCapabilitiesFromRegistry() {
-	typesRegistry := GetGlobalTypesRegistry()
-
-	var capabilities []types.TaskType
-	for taskType := range typesRegistry.GetAllDetectors() {
-		capabilities = append(capabilities, taskType)
-	}
-
-	// Set the default capabilities in the types package
-	types.SetDefaultCapabilities(capabilities)
-
-	glog.V(1).Infof("Set default worker capabilities from registry: %v", capabilities)
-}
-
-// BuildMaintenancePolicyFromTasks creates a maintenance policy with default configurations
-// from all registered tasks using their UI providers
-func BuildMaintenancePolicyFromTasks() *types.MaintenancePolicy {
-	policy := types.NewMaintenancePolicy()
-
-	// Get all registered task types from the UI registry
-	uiRegistry := GetGlobalUIRegistry()
-
-	for taskType, provider := range uiRegistry.GetAllProviders() {
-		// Get the default configuration from the UI provider
-		defaultConfig := provider.GetCurrentConfig()
-
-		// Set the configuration in the policy
-		policy.SetTaskConfig(taskType, defaultConfig)
-
-		glog.V(3).Infof("Added default config for task type %s to policy", taskType)
-	}
-
-	glog.V(2).Infof("Built maintenance policy with %d task configurations", len(policy.TaskConfigs))
-	return policy
-}
-
-// SetMaintenancePolicyFromTasks sets the default maintenance policy from registered tasks
-func SetMaintenancePolicyFromTasks() {
-	// This function can be called to initialize the policy from registered tasks
-	// For now, we'll just log that this should be called by the integration layer
-	glog.V(1).Infof("SetMaintenancePolicyFromTasks called - policy should be built by the integration layer")
-}
-
 // TaskRegistry manages task factories
 type TaskRegistry struct {
 	factories map[types.TaskType]types.TaskFactory