cleanup: remove #[serial] annotations from e2e_test, scanner, lifecycle, and object-capacity crates

Remove no-op #[serial] attributes (nextest ignores serial_test) and the
serial_test dependency from four crates. All tests already use temp_env
for env-var isolation, making #[serial] purely redundant.

Crates cleaned:
- e2e_test (37 annotations, 9 imports, removed serial_test dep)
- rustfs-scanner (115 annotations across 7 files, removed serial_test dep)
- rustfs-lifecycle (46 annotations, removed serial_test dep)
- rustfs-object-capacity (38 annotations, removed serial_test dep)

Also converted scanner/tests/lifecycle_integration_test.rs
with_forced_immediate_enqueue_timeout helper from unsafe raw
env::set_var/remove_var to temp_env::async_with_vars for proper
isolation, and added async_closure feature to scanner's temp-env dep.

Cargo.lock

@@ -3843,7 +3843,6 @@ dependencies = [
  "s3s",
  "serde",
  "serde_json",
- "serial_test",
  "sha2 0.11.0",
  "suppaftp",
  "time",
@@ -9804,7 +9803,6 @@ dependencies = [
  "rustfs-replication",
  "rustfs-storage-api",
  "s3s",
- "serial_test",
  "temp-env",
  "time",
  "tokio",
@@ -9920,7 +9918,6 @@ dependencies = [
  "rustfs-config",
  "rustfs-io-metrics",
  "rustfs-utils",
- "serial_test",
  "temp-env",
  "tempfile",
  "tokio",
@@ -10293,7 +10290,6 @@ dependencies = [
  "s3s",
  "serde",
  "serde_json",
- "serial_test",
  "sha2 0.11.0",
  "temp-env",
  "tempfile",