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/s3api/s3api_object_handlers_copy.go

@@ -14,8 +14,6 @@ import (
 	"strings"
 	"time"
 
-	"modernc.org/strutil"
-
 	"github.com/seaweedfs/seaweedfs/weed/filer"
 	"github.com/seaweedfs/seaweedfs/weed/glog"
 	"github.com/seaweedfs/seaweedfs/weed/operation"
@@ -797,58 +795,6 @@ func replaceDirective(reqHeader http.Header) (replaceMeta, replaceTagging bool)
 	return reqHeader.Get(s3_constants.AmzUserMetaDirective) == DirectiveReplace, reqHeader.Get(s3_constants.AmzObjectTaggingDirective) == DirectiveReplace
 }
 
-func processMetadata(reqHeader, existing http.Header, replaceMeta, replaceTagging bool, getTags func(parentDirectoryPath string, entryName string) (tags map[string]string, err error), dir, name string) (err error) {
-	if sc := reqHeader.Get(s3_constants.AmzStorageClass); len(sc) == 0 {
-		if sc := existing.Get(s3_constants.AmzStorageClass); len(sc) > 0 {
-			reqHeader.Set(s3_constants.AmzStorageClass, sc)
-		}
-	}
-
-	if !replaceMeta {
-		for header := range reqHeader {
-			if strings.HasPrefix(header, s3_constants.AmzUserMetaPrefix) {
-				delete(reqHeader, header)
-			}
-		}
-		for k, v := range existing {
-			if strings.HasPrefix(k, s3_constants.AmzUserMetaPrefix) {
-				reqHeader[k] = v
-			}
-		}
-	}
-
-	if !replaceTagging {
-		for header, _ := range reqHeader {
-			if strings.HasPrefix(header, s3_constants.AmzObjectTagging) {
-				delete(reqHeader, header)
-			}
-		}
-
-		found := false
-		for k, _ := range existing {
-			if strings.HasPrefix(k, s3_constants.AmzObjectTaggingPrefix) {
-				found = true
-				break
-			}
-		}
-
-		if found {
-			tags, err := getTags(dir, name)
-			if err != nil {
-				return err
-			}
-
-			var tagArr []string
-			for k, v := range tags {
-				tagArr = append(tagArr, fmt.Sprintf("%s=%s", k, v))
-			}
-			tagStr := strutil.JoinFields(tagArr, "&")
-			reqHeader.Set(s3_constants.AmzObjectTagging, tagStr)
-		}
-	}
-	return
-}
-
 func processMetadataBytes(reqHeader http.Header, existing map[string][]byte, replaceMeta, replaceTagging bool) (metadata map[string][]byte, err error) {
 	metadata = make(map[string][]byte)
 
@@ -2632,13 +2578,6 @@ func cleanupVersioningMetadata(metadata map[string][]byte) {
 	delete(metadata, s3_constants.ExtETagKey)
 }
 
-// shouldCreateVersionForCopy determines whether a version should be created during a copy operation
-// based on the destination bucket's versioning state.
-// Returns true only if versioning is explicitly "Enabled", not "Suspended" or unconfigured.
-func shouldCreateVersionForCopy(versioningState string) bool {
-	return versioningState == s3_constants.VersioningEnabled
-}
-
 // isOrphanedSSES3Header checks if a header is an orphaned SSE-S3 encryption header.
 // An orphaned header is one where the encryption indicator exists but the actual key is missing.
 // This can happen when an object was previously encrypted but then copied without encryption,