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.

crates/e2e_test/src/degraded_read_eof_regression_test.rs

@@ -55,7 +55,6 @@ mod tests {
     use aws_sdk_s3::Client;
     use aws_sdk_s3::primitives::ByteStream;
     use aws_sdk_s3::types::{CompletedMultipartUpload, CompletedPart};
-    use serial_test::serial;
     use sha2::{Digest, Sha256};
     use std::error::Error;
     use tokio::time::{Duration, timeout};
@@ -269,7 +268,6 @@ mod tests {
     /// stripes) and a multipart object (3 parts × 5 MiB) must GET back as a
     /// full, byte-identical body with the correct Content-Length. No early EOF.
     #[tokio::test]
-    #[serial]
     async fn degraded_read_large_objects_with_one_disk_offline_return_full_body() -> TestResult {
         init_logging();
         info!("dist-13 (a): large-object degraded read with one of four disks offline");
@@ -335,7 +333,6 @@ mod tests {
     /// mid-stream — the exact window the fixes had to reconstruct through rather
     /// than truncate.
     #[tokio::test]
-    #[serial]
     async fn degraded_read_reconstructs_through_midstream_bitrot_within_quorum() -> TestResult {
         init_logging();
         info!("dist-13 (b): mid-stream bitrot within quorum must reconstruct a full body");
@@ -393,7 +390,6 @@ mod tests {
     /// Content-Length. `get_checked` panics on that forbidden outcome, so this
     /// test fails loudly if the truncation bug ever returns.
     #[tokio::test]
-    #[serial]
     async fn beyond_quorum_degraded_read_never_silently_truncates() -> TestResult {
         init_logging();
         info!("dist-13 (c): beyond-quorum degraded read must fail, never 200+truncated");