Removes the remaining 230 no-op `#[serial]` markers across 77 files, plus the 77 imports that went with them. Stacked on the six-suite batch; together they take `crates/e2e_test` from 345 markers to 36.
The reasoning is unchanged from #6209: `#[serial]` is an in-process mutex and cargo-nextest gives every test its own process, so only a `[test-groups]` binding with `max-threads = 1` serializes anything.
Everything still carrying a marker now has a reason to:
inline_fast_path_cluster_test 14 test-group e2e-inline-boundaries
policy/policy_variables_test 6 binds a fixed port
kms/kms_vault_test 5 test-group e2e-vault
reliability_disk_fault_test 4 test-group e2e-reliability
degraded_read_eof_regression_test 3 test-group e2e-reliability
replacement_privileged_e2e_test 2 test-group e2e-reliability
protocols/webdav_core 1 binds fixed ports
policy/test_runner 1 binds a fixed port
The three fixed-port files are held back rather than swept, because their markers are not merely useless: `PolicyTestEnvironment::with_address("127.0.0.1:9000")` and webdav_core's `127.0.0.1:9080`/`:9010` bind fixed ports, which an in-process mutex cannot protect against a second test process. They need a test-group, which is a config change rather than a deletion, so it is filed on the issue instead.
`security_boundary_test` was checked and swept: its `127.0.0.1:8080` strings are SSRF targets fed to AddTier in a negative test, not ports it binds.
Refs backlog#1846 (T1)
Zhengchao An